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Context: Thyroid-stimulating hormone (TSH) trajectory classification represents a novel approach to defining the adequacy of levothyroxine (LT4) treatment for hypothyroidism over time., Objective: This is a proof of principle study that uses longitudinal clinical data, including thyroid hormone levels from a large prospective study to define classes of TSH trajectories and examine changes in cardiovascular (CV) health markers over the study period., Methods: Growth mixture modeling (GMM), including latent class growth analysis (LCGA), was used to classify LT4-treated individuals participating in the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil) based on serial TSH levels. Repeated measure analyses were then utilized to assess within-class changes in blood pressure, lipid levels, hemoglobin A1c, and CV-related medication utilization., Results: From the 621 LT4-treated study participants, the best-fit GMM approach identified 4 TSH trajectory classes, as defined by their relationship to the normal TSH range: (1) high-high normal TSH, (2) normal TSH, (3) normal to low TSH, and (4) low to normal TSH. Notably, the average baseline LT4 dose was lowest in the high-high normal TSH group (77.7 µg, P < .001). There were no significant differences in CV health markers between the classes at baseline. At least 1 significant difference in CV markers occurred in all classes, highlighted by the low to normal class, in which total and high-density lipoprotein cholesterol, triglycerides, and A1c all increased significantly (P = .049, P < .001, P < .001, and P = .001, respectively). Utilization of antihypertensive, antihyperlipidemic, and antidiabetes medications increased in all classes., Conclusion: GMM/LCGA represents a viable approach to define and examine LT4 treatment by TSH trajectory. More comprehensive datasets should allow for more complex trajectory modeling and analysis of clinical outcome differences between trajectory classes., (© The Author(s) 2024. Published by Oxford University Press on behalf of the Endocrine Society. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.)

In light of research indicating that normal TSH levels do not necessarily reflect clinical euthyroidism in hypothyroid patients, and given the patient dissatisfaction with levothyroxine (LT4) monotherapy, we evaluate the response to weight loss treatment in patients with obesity and primary hypothyroidism who are euthyroid under LT4 therapy, with a focus on weight and metabolic parameters. The retrospective study included 138 subjects with obesity (BMI ≥ 30 kg/m 2 ), 69 women with hypothyroidism on levothyroxine, and 69 age- and BMI-matched women without thyroid disease. Secondary causes of obesity, medications that may affect thyroid functions and metabolic parameters, chronic and oncological disease, pregnancy, TSH outside the reference range, follow-up periods of less than one year, and bariatric surgery were the exclusion criteria. Patients' characteristics and metabolic responses to weight reduction treatment consisting of calorie restriction, moderate exercise, and metformin if needed were evaluated. TSH and fT4 levels were higher, and fT3 and T3/T4 ratios were lower all within the reference ranges in hypothyroid women. They were less insulin resistant. Both patient' groups experienced a significant decrease in body weight, BMI, and atherogenic index of plasma (AIP) during the follow-up (p = 0.001). Insulin resistance was not changed. The groups' body weight, BMI, HOMA-IR, and AIP changes were similar at the end of the study (p = 0.876, p = 0.850, p = 0.555, p = 0.293). The results suggest that achieving euthyroid status via levothyroxine monotherapy in hypothyroid women leads to weight loss responses comparable to those in women with normal thyroid. This supports the effectiveness of current hypothyroidism treatment strategies, emphasizing TSH level normalization, in achieving clinical euthyroidism concerning weight loss outcomes., Competing Interests: Declarations Competing interests The authors declare no competing interests., (© 2024. The Author(s).)

Objective: As thionamide is associated with various adverse effects, we re-evaluated the practical efficacy of potassium iodide (KI) therapy for Graves' hyperthyroidism (GD)., Methods: We administered KI (mainly 100 mg/day) to 324 untreated GD patients and added methimazole (MMI) only to those remaining thyrotoxic even at 200 mg/day. When the patient became hypothyroid, MMI, if taken was stopped, then levothyroxine (LT4) was added without reducing the KI dose. Radioactive iodine (RI) therapy or thyroidectomy was performed whenever required. We evaluated the early effects of KI at 2-4 weeks and followed patients for 2 years., Results: At 2 weeks, serum thyroid hormone levels decreased in all 324 patients. At 4 weeks, fT4, fT3, and both fT4 and fT3 levels became normal or low in 74.7%, 50.6%, and 50.6% of patients, respectively. In a cross-sectional survey over 2 years, GD was well-controlled with KI or KI + LT4 (KI-effective) in >50% of patients at all time points. Among 288 patients followed for 2 years, 42.7% remained 'KI-effective' throughout the 2 years (KI Group), 30.9% were well-controlled with additional MMI given for 1-24 months, and 26.4% were successfully treated with ablative therapy (mainly RI). Among 'KI-effective' patients at 4 weeks, 76.5% were classified into the KI Group. No patients experienced adverse effects from KI., Conclusion: KI therapy was useful in the treatment of GD. A sufficient dose of KI was effective in >50% of GD patients from 4 weeks to 2 years, and 42.7% (76.5% of 'KI-effective' patients at 4 weeks) remained 'KI-effective' throughout the 2 years.

Following implementation of a national prevention program against iodine deficiency-related disorders in 1993 in Germany, the prevalence of thyroid disorders declined, but aggregated drug dispensation data suggested a recent increase in thyroid hormone use. We aimed to systematically investigate trends in the use of thyroid diagnostic and treatment measures between 2008 and 2019 in Germany. Using the GePaRD database (claims data from ~ 20% of the German population), we determined the annual age-specific and age-standardized prevalence of the use of thyroid diagnostics (thyroid-stimulating hormone (TSH) measurement, thyroid ultrasound, scintiscan, biopsy) and treatment (medication, surgery, radioiodine therapy) from 2008 to 2019 stratified by sex. Between 2008 and 2019, the age-standardized prevalence of TSH measurement increased by 44% in males (from 165 to 238 per 1,000 persons) and by 31% in females (from 134 to 176 per 1,000). The prevalence of thyroid ultrasound use showed no clear time trend, while there was a decrease in the prevalence of scintiscan use (males/females: decrease by 42/43%) and biopsy (males/females: decrease by 42/34%). The prevalence of levothyroxine use increased by ~ 31% both in males (from 36 to 47 per 1,000) and females (from 134 to 175 per 1,000), while the prevalence of thionamide use, iodine use, thyroidectomy, and radioiodine therapy decreased. Our study suggests a continued decline in the prevalence of clinically significant thyroid disorders between 2008 and 2019. The substantial increase in the prevalence of TSH measurement and levothyroxine use during this time period might indicate overuse of diagnostics and overtreatment, warranting further investigation., (© 2024. The Author(s).)

Objective: To evaluate the combined administration of propylthiouracil (PTU) and levothyroxine (LT4) in managing monocarboxylate transporter 8 (MCT8) deficiency and identify optimal therapeutic dosages. Methods: This multicenter case series involved 12 male patients with MCT8 deficiency whose parents/guardians consented to PTU and LT4 treatment. Data were collected from January 2008 to June 24, 2024. The study focused on treatment safety and outcomes, analyzing baseline and last encounter biochemical, metabolic, and anthropometric parameters. Statistical analyses included Wilcoxon signed ranks tests and generalized estimated equations to assess effects on thyroid and metabolic markers, and receiver operating characteristics curves to predict optimal dose. Results: Patients showed a significant reduction in serum total triiodothyronine (TT3) concentration and TT3/TT4 ratio, with increased serum TT4 and free T4 (fT4) concentrations. The use of PTU effectively reduced TT3 concentration by 25% at an average dose of 6.8 mg/kg/day, while LT4 increased fT4 concentration by 40% from baseline at an average dose of 4.3 µg/kg/day. Thyrotropin concentration was undetectable on treatment. No statistical differences were observed in metabolic and physical parameters between baseline and last encounter overall for the group, but six of eight patients for whom these data were available had an increase in weight ( z -score). There were no adverse effects on liver function or granulocyte numbers noted throughout the period of observation. Conclusion: Combined treatment with PTU and LT4 normalized serum T3, fT4, and TT4 in patients with MCT8 deficiency. Individualized dose adjustments were crucial for achieving therapeutic goals, indicating the need for personalized treatment plans.

Persistent symptoms are common in the general population and even more so in people with hypothyroidism. When symptoms are unexplained and brought to medical attention, they can be referred to as medically not yet explained symptoms (MNYES), a term preferred to other descriptors by patients, care-givers and experts. MNYES might be neglected by endocrinologists or misattributed to hypothyroidism. Awareness of MNYES could open up more effective and less harmful interventions for patients who present to endocrinologists with unexplained symptoms than costly over-investigations and over-treatment with thyroid hormones (such as levothyroxine and liothyronine). The role of the endocrinologist is to recognize and acknowledge that MNYES could be underlying a patient's presentation, to communicate effectively with the patient and others involved in the patient's care, to apply a 'two-track approach' in management by paying equal attention to physical and psychosocial contributors, and to collaborate with other relevant health professionals. Categorization of patients into levels of risk for symptom deterioration helps in selecting suitable therapies. Effective management of MNYES demands time, training, expertise and resources., (© 2024. Springer Nature Limited.)

Background: NKX2-1, a crucial transcription factor in thyroid, lung, and brain development, is associated with rare disorders featuring thyroid dysfunction, neurological abnormalities, and respiratory symptoms. The primary challenge in managing NKX2-1-related disorders (NKX2-1-RD) is early diagnosis of the genetic defect and treating specific endocrine disorders. Levothyroxine (LT4) serves as the standard hypothyroidism treatment, with required dosages influenced by the severity of the individual's disorder, which varies widely among affected individuals., Objectives: This systematic review aims to assess the effectiveness of LT4 treatment in NKX2-1-RD and explore optimal dosing strategies. The primary focus is on the challenges associated with the prompt diagnosis of genetic defects, rather than the established treatment protocols for individual endocrine failures., Methods: Adhering to PRISMA guidelines, the review includes 42 studies involving 110 genetically confirmed NKX2-1-RD patients with hypothyroidism. The study investigates congenital hypothyroidism as the most prevalent endocrine alteration, along with gestational and overt hypothyroidism. The administration of LT4 treatment, dosages, and patient responses are analyzed., Results: Among the findings, congenital hypothyroidism emerges as the predominant endocrine alteration in 41% of patients. Notably, LT4 treatment is administered in only 10% of cases, with a mean dose of 52 μg/day. The variability in initiation and dosage is likely influenced by the age at diagnosis. Positive responses, characterized by TSH adjustments within normal ranges, are observed in 11 monitored patients., Conclusions: Early detection of congenital hypothyroidism is emphasized for timely LT4 initiation. Challenges in standardization are highlighted due to the variability in clinical manifestations and diagnostic procedures across NKX2-1-RD cases. While this review provides valuable insights into thyroid and pituitary disease treatment, limited details on LT4 treatment represent a significant study limitation. Key reporting points for future case studies are proposed to enhance the understanding and management of NKX2-1-RD hypothyroidism., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2024 Carmona-Hidalgo et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Background: Long-term management of patients with hypothyroidism on thyroxine replacement requires thyroid function test (TFT) monitoring once every six-12 months as recommended by clinical practice guidelines. This study determined their thyroid function status during two-year follow-up visits in primary care, and the factors influencing their thyroid status, and assessed the optimal interval for TFTs., Methods: A retrospective cohort study was conducted on adults with a clinical diagnosis code for hypothyroidism in their electronic health records taken from a group of polyclinics in Singapore between July 2017 and June 2020. The follow-up thyroid status was categorized as under-replacement (TSH ≥ 3.70mIU/L), over-replacement (TSH ≤ 0.65mIU/L) or euthyroid (TSH 0.65-3.70mIU/L). The patients' demographic, clinical and TFT data were analyzed using appropriate statistical tests during the two-year follow-up. Stepwise logistic regression analysis identified the factors associated with suboptimal thyroid control. Kaplan-Meier analysis was used to compare their thyroid function status in association with the interval between TFT monitoring., Results: Data from 5,749 eligible subjects (mean age 62.1 ± 13.29 years; 79% female; 79.7% Chinese) were analyzed. After a two-year follow-up, 61.9% (n = 3558) of all subjects were euthyroid, with 29.5% (n = 1694) being under-replaced and 8.6% (n = 497) over-replaced. However, thyroid status did not differ significantly with the various dose regimen (daily, segmented, or alternate days) (p = 0.193). Stepwise logistic regression showed that thyroxine under-replacement was significantly associated with the male gender (AOR = 1.25,95%CI = 1.03-1.51,p = 0.02) and obesity (AOR = 1.34,95%CI = 1.08-1.66,p = 0.008). Every unit (μg/kg body weight) increase in the mean daily thyroxine dose was associated with 2.72 times greater odds of over-replacement. When comparing thyroid function monitoring at intervals of 13-24 months, monitoring at shorter intervals (≤ 12 months) was less likely to detect thyroxine under-replacement (AOR = 0.57,95%CI = 0.44-0.74,p < 0.001) and over-replacement (AOR = 0.62,95%CI = 0.41-0.97,p = 0.033). Among the 3,312 adults who were euthyroid at baseline, 22.2%, 41.7% and 59.6% had suboptimal thyroid control at 6, 12 and 24 months respectively (Kaplan-Meier analysis)., Conclusion: Around six in ten patients were euthyroid with thyroxine replacement for hypothyroidism in primary care over two years. Thyroxine under-replacement was associated with male gender and obesity. The proportion of euthyroid patients developing abnormal thyroid function doubled with TFTs at six, 12 and 24-month intervals., (© 2024. The Author(s).)

Alzheimer's disease (AD) poses a major challenge due to its impact on the elderly population and the lack of effective early diagnosis and treatment options. In an effort to address this issue, a study focused on identifying potential biomarkers and therapeutic agents for AD was carried out. Using RNA-Seq data from AD patients and healthy individuals, 12 differentially expressed genes (DEGs) were identified, with 9 expressing upregulation (ISG15, HRNR, MTATP8P1, MTCO3P12, DTHD1, DCX, ST8SIA2, NNAT, and PCDH11Y) and 3 expressing downregulation (LTF, XIST, and TTR). Among them, TTR exhibited the lowest gene expression profile. Interestingly, functional analysis tied TTR to amyloid fiber formation and neutrophil degranulation through enrichment analysis. These findings suggested the potential of TTR as a diagnostic biomarker for AD. Additionally, druggability analysis revealed that the FDA-approved drug Levothyroxine might be effective against the Transthyretin protein encoded by the TTR gene. Molecular docking and dynamics simulation studies of Levothyroxine and Transthyretin suggested that this drug could be repurposed to treat AD. However, additional studies using in vitro and in vivo models are necessary before these findings can be applied in clinical applications., (© 2024. The Author(s).)

Rationale: Programmed cell death (PD) -1 inhibitors has significantly improved the prognosis of cancer patients by enhancing antitumor immune responses. However, PD-1 inhibitors are associated with immune-related adverse events, some of which are rare and potentially life-threatening. Thus far, elevated creatine kinase (CK) and creatinine caused by a novel PD-1 inhibitor (sintilimab)-induced hypothyroidism has not yet been reported., Patient Concerns: A 63-year-old male patient with esophageal cancer who developed hypothyroidism accompanied by unexplained increases in CK and creatinine after sintilimab treatment., Diagnosis: Since the increases in CK and creatinine paralleled the decrease in thyroxine, after excluding other potential conditions, we speculated that the muscular and renal dysfunction might be caused by sintilimab-induced hypothyroidism., Interventions and Outcomes: As the patient's thyroid function improved with levothyroxine replacement therapy, the levels of CK and creatinine concomitantly returned to normal., Conclusion and Lessons: The elevated CK and creatinine levels in this patient were caused by sintilimab-induced hypothyroidism. Our case highlights the importance of keeping PD-1 induced hypothyroidism in mind when patients present with unexplained increased levels of CK and creatinine. Hypothyroidism-related muscular and renal dysfunctions, which can be restored with thyroid hormone replacement, need to be identified early and treated promptly so that unnecessary examinations and treatments can be avoided in these patients., Competing Interests: The authors have no funding and conflicts of interest to disclose., (Copyright © 2024 the Author(s). Published by Wolters Kluwer Health, Inc.)

The androgen receptor signaling inhibitor apalutamide is used successfully for the treatment of prostate cancer. An increased risk of hypothyroidism, mostly subclinical, has been reported in the SPARTAN and TITAN trials. We present three cases of subacute deterioration of previously known but well-controlled hypothyroidism treated with levothyroxine, occurring shortly after the initiation of treatment with apalutamide, resulting in severe hypothyroidism. These cases highlight the importance of awareness of thyroid dysfunction during treatment with apalutamide, particularly in patients with pre-existing thyroid disease, common in the general population. We provide practice recommendations for thyroid management prior to and during apalutamide treatment as well as after the interruption of this therapy.

Objective: There are few reports of subacute thyroiditis (SAT) during pregnancy. This study aimed to clarify the clinical characteristics of SAT in pregnant patients., Methods and Results: Seven patients diagnosed with SAT during pregnancy at our institution from January 2004 to December 2021 were identified, and their clinical findings were retrospectively examined. At SAT diagnosis, the median age was 34 (range: 31-42) years, the median duration of pregnancy was 5 (4-24) weeks, and all patients had neck pain but no fever. On laboratory examination, median (range) free thyroxine, free triiodothyronine, and C-reactive protein levels were 2.66 (1.14-7.77) ng/dL, 7.1 (3.3-16.1) pg/mL, and 2.22 (0.42-5.79) mg/dL, respectively, and all patients had a hypoechoic lesion of the thyroid gland. Three patients (43%) were treated with steroids, and three patients (43%) received replacement therapy with levothyroxine for hypothyroidism following destructive thyroiditis. There were no pregnancy complications in any of the cases. These seven patients (pregnancy group) were compared with 217 non-pregnant female patients (non-pregnancy group) aged 31 to 42 years who were diagnosed with SAT at our institution from 2016 to 2019. The frequency of body temperatures above 37°C was lower in the pregnancy group than in the non-pregnancy group (0% vs 65%)., Conclusion: Patients who develop SAT during pregnancy may have less fever than non-pregnant patients with SAT. There were no pregnancy complications in the pregnancy group in this study. This suggests that adverse pregnancy outcomes may be avoided by the appropriate management of SAT, including hypothyroidism after destructive thyroiditis.

Hypothyroidism, the deficiency of thyroid hormone, is a common condition worldwide. It affects almost all body systems and has a wide variety of clinical presentations from being asymptomatic to, in rare cases, life threatening. The classic symptoms of hypothyroidism include fatigue, lethargy, weight gain, and cold intolerance; however, these symptoms are non-specific and the diagnosis is typically made on biochemical grounds through serum thyroid function tests. The most common cause of hypothyroidism is chronic autoimmune thyroiditis (Hashimoto's thyroiditis), although other causes, including drugs (such as amiodarone, lithium, and immune checkpoint inhibitors), radioactive-iodine treatment, and thyroid surgery, are frequent. Historically, severe iodine deficiency was the most common cause. Reference ranges for thyroid function tests are based on fixed percentiles of the population distribution, but there is increasing awareness of the need for more individualised reference intervals based on key factors such as age, sex, and special circumstances such as pregnancy. Levothyroxine monotherapy is the standard treatment for hypothyroidism; it is safe and inexpensive, restores thyroid function tests to within the reference range, and improves symptoms in the majority of patients. However, 10% of patients have persistent symptoms of ill health despite normalisation of thyroid function tests biochemically and a substantial proportion of patients on levothyroxine have thyroid-stimulating hormone concentrations outside the reference range. Ongoing symptoms despite levothyroxine treatment has led to some patients using liothyronine or desiccated thyroid extract. Taken together, these factors have led to intense debate around the treatment thresholds and treatment strategies for hypothyroidism. In this Seminar, we review the epidemiology, genetic determinants, causes, and presentation of hypothyroidism; highlight key considerations and controversies in its diagnosis and management; and provide future directions for research., Competing Interests: Declaration of interests PNT has received funds from the British Thyroid Foundation and the Association of Physicians of GB & Ireland for studies on hypothyroidism, and from PassPACES as an examiner. He received a Leadership and Development Award from the Society for Endocrinology; is Chair of the Welsh Endocrine and Diabetes Society; a member of UK Iodine; and is a member of the British Thyroid Association executive committee. MMM has received financial support from ACE Pharmaceuticals (Zeewolde, the Netherlands) for a randomised controlled trial of levothyroxine–liothyronine replacement in patients with hypothyroidism. AH-D is Principal Investigator and member of the steering committee of the HORIZON 2020 EUThyroid grant; coordinator and Primary Investigator of the GRAN-T-MTC (ERA-NET FP7) grant and the HORIZON 2020 TECANT grant; has received consulting fees and travel support for expert meeting attendance from Institut Biochimique (IBSA) and Recordati; has received speaker honoraria from IBSA, Ipsen, Novartis, Merck, Berlin Chemie—Menarini, and Pfizer; is President of the Polish Society of Endocrinology, Chairperson of the Polish Commission for the Control of Iodine Deficiency Disorders, and Team Leader for the Polish Society of Endocrinology guidelines for the diagnosis and treatment of thyroid diseases; and has participated in an advisory board for Ipsen. KB is President of the British Thyroid Association, Chair of the Clinical Committee and Council Member of the Society for Endocrinology, member of the European Thyroid Association executive committee, and member of the programme organising committee of the American Thyroid Association; she has received grant funding from the National Institute for Health and Care Research (NIHR), Research for Patient Benefit (NIHR200772) and NIHR Health Technology Assessment (NIHR135261); she has received consulting fees from Eli Lilly, Eisai, SERB, Egetis Pharmaceuticals, and the Medicines and Healthcare products Regulatory Agency; she has received speaker honoraria from the Emirates Diabetes and Endocrine Society and Eisai; she has received editor honoraria from Best Practice and Research Clinical Endocrinology and Metabolism, and honoraria from NICE as clinical lead for the Thyroid Diseases guidelines; she was the recipient of the Society for Endocrinology Outstanding Clinical Practitioner Award; she is Associate Editor for the Journal of the Endocrine Society for which she receives honoraria; and is on the international advisory board for The Lancet Diabetes & Endocrinology., (Copyright © 2024 Elsevier Ltd. All rights reserved, including those for text and data mining, AI training, and similar technologies.)

Background: Scales are composed of exfoliated keratinocytes and are frequently a secondary change, requiring the determination of the underlying cause. Consequently, making an appropriate differential diagnosis of scales and determining treatment necessity based on the results is crucial in dermatological practice., Case Description: We present a 7-year-old, neutered male Toy Poodle examined at Myogadani Animal Hospital with chief complaints of exercise intolerance, unexplained weight gain, and dermatological signs, including symmetrical alopecia of the trunk. The dog was diagnosed with hypothyroidism and administered levothyroxine sodium. A significant number of scales were observed, primarily on the trunk, after 1 month of administration. The scales disappeared after only reducing the dose of levothyroxine sodium for 3 months. Additionally, hair regrowth was observed as the scales disappeared. In this case, the scales were primarily observed in the alopecia area of the trunk, where hair growth was subsequently noted. Hence, levothyroxine sodium administration was thought to not only facilitate hair regrowth but also influence skin turnover, causing the appearance of scales., Conclusion: Clinicians who treat hypothyroidism need to be cognizant that symmetrical scales, primarily located on the trunk, do not co-occur with other skin lesions, such as erythema, and are not itchy, may appear within a month. The scales will naturally disappear in such cases when hair growth is complete; thus, no additional treatment is required., Competing Interests: The authors declare that there is no conflict of interest.

Background: Patients treated for hypothyroidism with levothyroxine (LT4) monotherapy may present with persistent hypothyroidism symptoms, including cognitive symptoms, despite having a normal thyroid stimulating hormone (TSH) level. It remains unclear whether LT4 monotherapy is sufficient to normalize cognitive function outcomes over time. Methods: This is a multisite longitudinal study of a diverse group of women during midlife representing 5 ethnic/racial groups from 7 enrollment sites across the United States in the Study of Women's Health Across the Nation. Women were screened for a history of thyroid disease and the use of LT4. The study consisted of two primary groups: women with LT4-treated hypothyroidism and control women without thyroid disease. Each participant completed up to 9 cognitive assessments over the study period testing processing speed, working memory, and episodic memory (immediate and delayed recall). Multivariable generalized linear mixed models of scores for each cognitive assessment were developed to determine the association between LT4-treated hypothyroidism and cognitive function trajectories. Covariates included sociodemographic, clinical characteristics, and menopausal status (pre/early peri, late peri, and surgical/post). Sensitivity analyses were conducted to assess the impact of abnormal TSH levels and practice effects (i.e., improvements in scoring after repeated testing). Results: Of the 2033 women who were included in the study, 227 (11.2%) met criteria for LT4-treated hypothyroidism. At baseline, both processing speed and working memory scores were higher in LT4-treated women (mean processing speed scores: 56.5 vs 54.4; p value = 0.006; mean working memory scores: 6.8 vs 6.4; p value = 0.018). However, when considering the effect of LT4-treated hypothyroidism over time, there were no significant differences in the rate of cognitive decline (in any measure) between the hypothyroidism and control groups with or without covariate adjustment. The results were similar when considering LT4-treated women with abnormal TSH levels or after minimizing practice effects. Conclusions: We observed no difference in cognitive decline between women with LT4-treated hypothyroidism and women without thyroid disease. For similar aged patients with cognitive complaints, if thyroid function testing is normal, clinicians should consider causes other than inadequate thyroid hormone treatment to explain these symptoms.

There is a close relationship between thyroid dysfunction and renal dysfunction. However, thyroid dysfunction can unfortunately result in inaccurate measurements of serum creatinine and cystatin C levels. The chronic decrease in cardiac output due to hypothyroidism can reduce renal plasma flow (RPF) resulting in renal dysfunction. We report the case of a 36-year-old male in whom renal dysfunction detected during a company health check-up was found to be caused by severe hypothyroidism. His serum creatinine levels showed poor results, but serum cystatin C levels were within the normal range. The physician thus prioritized serum cystatin C for assessing the patient's renal function, and concluded that his renal function was normal. He subsequently visited our hospital, aged 36 years, for a comprehensive examination. His serum creatinine level was 1.88 mg/dL and his serum cystatin C level was 0.75 mg/dL, indicating an unusual discrepancy between the two measurements. The patient also presented with fatigue, suggesting hypothyroidism, and we therefore evaluated his thyroid function. His free thyroxine level was below the sensitivity of the assay, while his thyroid-stimulating hormone level was > 100 μIU/mL. A renal biopsy was performed to further explore the underlying cause of his renal dysfunction, which suggested that reduced RPF could be the leading cause of his renal ischemia, with no indications of chronic glomerulonephritis or other abnormalities. His hypothyroidism and renal function improved after thyroid hormone replacement therapy. Given the limited reports of renal biopsy tissue examination during the acute phase of hypothyroidism, the current case provides important information regarding the diagnosis of renal dysfunction in patients with hypothyroidism., (© 2024. The Author(s).)

The COVID-19 pandemic was a major challenge for all health care employees, but it was also difficult for patients to gain access to health care services. Myxedema coma (MC) is an extremely rare but potentially fatal endocrine emergency. The aim of the study was to report an increased incidence of life-threatening myxedema coma that occurred in relation to the COVID-19 pandemic. In this paper, we report a cohort of 11 patients with MC who were treated at the University Hospital in Krakow, Poland, in the period from 2015 to 2023. Only 1 case of MC was recorded in the period from 2015 to 2019, and, in the same area, 10 cases of MC were recorded after the start of COVID-19 pandemic until present. Hypothyroidism was diagnosed de novo in 2 (18%) patients; the remaining patients were severely hypothyroid due to therapy non-compliance. Nine patients had primary hypothyroidism, and 2 had central hypothyroidism. Besides longstanding hypothyroidism, an additional precipitating factor for MC was identified in 4 (36%) of the patients. Due to the inaccessibility of parenteral levothyroxine, patients were treated with oral, mostly liquid, form of levothyroxine. The mortality rate in this cohort was 27.2%. In conclusion, the increase of the incidence of MC, which is a life-threatening complication of inadequately treated hypothyroidism, during the COVID-19 pandemic, when resources were limited, and in the post-pandemic era, underlines the importance of adequate communication with patients and of long-term availability of primary care for patients with thyroid disease., (© 2024. The Author(s).)

Background: Thyroid dysfunction plays an important role in the pathology of diabetes-associated cognitive dysfunction (DACD). However, thyroid hormone (TH) signaling and action changes in DACD brains remain unknown. This study evaluated the alternations in TH signaling and action in the brains of DACD mice and explored the beneficial effects of levothyroxine (L-T4) treatment. Methods: KK-Ay mice, serving as a spontaneous type 2 diabetes mellitus model, underwent intragastric administration of 10 ng/g and 20 ng/g of L-T4 solution or normal saline for 8 weeks. Age-matched C57BL/6J mice were used as normal controls. Cognitive and memory functions were examined through the open field and Morris water maze tests. Hippocampal TH signaling and pathogenic status were evaluated. The potential signaling pathways involved in the neuroprotective action of L-T4 were investigated through RNA sequencing and further verified through quantitative real-time PCR (qPCR), Western blotting (WB), immunofluorescence (IF), and fluorescent multiplex immunohistochemistry (mIHC) in vivo and vitro. Results: The expressions of hippocampal TH transporters (Mct8 and Oatp1c1), Dio2, and TH receptor were upregulated, whereas Dio3 as well as the TH-positive regulated genes MBP, Enpp2, and Klf9 were downregulated in DACD mice. Exogenous L-T4 partially alleviated cognitive and memory dysfunction and restored hippocampal neuronal activity by optimizing TH signaling. RNA sequencing provided insights into the role of type I interferon (IFN-I) signaling and necroptosis on the amelioration of hippocampal damage after L-T4 treatment. WB and qPCR further confirmed that the levels of key proteins for IFN-I signaling and necroptosis (p-STAT1, p-STAT2, IRF9, ZBP1, p-RIP3, and p-MLKL) were increased, but largely returned after L-T4 administration in vivo and T3 treatment in vitro . IF and mIHC revealed that IRF9 and p-MLKL colocalized in neurons, but not in astrocytes or microglia, of the hippocampus in DACD mice. The diabetes mellitus group had an increased number of IRF9 + p-MLKL + NeuN + cells, which decreased after L-T4 treatment. The elevated IFN-I signaling-mediated necroptosis in HT22 cells was also decreased by T3. Conclusion: We demonstrated abnormal hippocampal TH signaling and action in DACD. Promoting TH action with exogenous L-T4 ameliorated hippocampal impairment through inhibiting IFN-I signaling-induced necroptosis.

Purpose: Recommended pharmacotherapy for hypothyroidism in Hashimoto's thyroiditis (HT) is oral supplementation with levothyroxine (LT-4). However, serum thyrotropin (TSH) levels within normal range are not consistently achieved with LT-4 medication., Patients and Methods: We report on 35 HT patients with LT-4 therapy in this retrospective evaluation. In general, we recommend that a maximum of two sips of water, which would then amount to < 50 mL, be ingested at the same time as LT-4. We report on follow up examinations measuring TSH and antibodies against thyroid peroxidase (TPOAb) after 6 months to five years., Results: After median time of 643 days (range 98-1825) we found in 35 HT patients a statistical significant reduction of serum TSH (p < 0.001) and TPOAb (p = 0.006). The patients median body weight was 71 kg (range 48-98) and a daily LT-4 dosage was used with median 69.1 µg (range 25-150). This results in a daily LT-4 dose of median 1.01 µg/kg bodyweight (range 0.3-2.3)., Conclusions: The reduction of water ingestion to a maximum of two sips, which is <50 mL, combined with LT-4 supplementation helps to achieve euthyroidism in HT. In addition, it reduces the L-T4 medication dosage needed to lower TSH serum levels and decreases TPO antibodies in HT., (© 2024. The Author(s).)

Importance: There is uncertainty as to whether treatment of subclinical hypothyroidism (SCH) is associated with cardiovascular outcomes. Objectives: To determine whether levothyroxine replacement therapy decreases the risk of major adverse cardiovascular events (MACE) among individuals with SCH defined as having a thyrotropin (TSH) level between 5 and 10 mU/L. Design: We conducted a population-based cohort study using a prevalent new-user design. Setting: The study utilized data from the United Kingdom Clinical Practice Research Datalink. Participants: We identified a base cohort of individuals aged ≥18 years with incident SCH defined as having at least two TSH levels between 5 and 10 mU/L within one year between 1998 and 2018. We matched 76,946 levothyroxine treated to 76,946 untreated individuals based on age, sex, calendar time, duration of SCH, and time-conditional propensity score. We compared individuals with SCH treated with levothyroxine with individuals with no treatment. Exposure: Levothyroxine treatment versus no treatment. Main Outcome Measures: The primary outcome, MACE, was defined as a composite of nonfatal myocardial infarction, nonfatal ischemic stroke, and cardiovascular-related mortality. Results: The mean age of the study cohort was 62.8 years, and 76.5% were women. During a median follow-up time of 1.6 years (interquartile range: 0.5-4.2), the incidence rate for MACE among individuals treated with levothyroxine was 12.8 per 1000 person-years; confidence interval (CI): 12.2-13.3 and 13.9 per 1000 person-years; CI: 13.4-14.3 among nontreated individuals. Levothyroxine treatment was associated with a small decreased risk of MACE (hazard ratio: 0.88; CI: 0.83-0.93). Conclusions: Levothyroxine treatment of SCH was associated with a small decreased risk of MACE. However, given the observational nature of the study, residual confounding should be considered in the interpretation of this finding.

Context: The effectiveness of levothyroxine (LT4) in restoring thyroid hormone (TH) homeostasis, particularly serum thyroxine (T4) and triiodothyronine (T3) levels, remains debatable., Objective: This work aimed to assess TH homeostasis in LT4-treated individuals using data from the Longitudinal Study of Adult Health in Brazil (ELSA-Brasil) study., Methods: The ELSA-Brasil study follows 15 105 adult Brazilians (aged 35-74 years) over 8.2 years (2008-2019) with 3 observation points assessing health parameters including serum thyrotropin (TSH), free T4 (FT4), and free T3 (FT3) levels. We analyzed 186 participants that initiated treatment with LT4 during the study, and 243 individuals continuously treated with LT4 therapy., Results: Initiation of therapy with LT4 resulted in an 11% to 19% decrease in TSH, an approximately 19% increase in FT4, and a 7% reduction in FT3 serum levels (FT3 dropped >10% in ∼40% of the LT4-treated patients). This was associated with an increase in triglyceride levels and utilization of hypolipidemic and antidiabetic medications. Participants continuously treated with LT4 exhibited a stable elevation in serum FT4 and a reduction in serum FT3 and TSH levels. While 115 participants (47.3%) had at least 1 serum FT4 levels above the control reference range (>1.52 ng/dL), 38 participants (15.6%) had at least 1 serum FT3 below the reference range (<0.23 ng/dL)., Conclusion: The present results challenge the dogma that treatment with LT4 for hypothyroidism restores TH homeostasis in all patients. A substantial number of LT4-treated patients exhibit repeated FT4 and FT3 levels outside the normal reference range, despite normal TSH levels. Further studies are needed to define the clinical implications of these findings., (© The Author(s) 2024. Published by Oxford University Press on behalf of the Endocrine Society. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.)

Background: The thyroid gland is an endocrine gland that has an impact on the body's general metabolism. Thus, the secretions of the thyroid gland can modify the overall metabolism of the entire body. The prevalence of hypothyroidism is increasing quickly, with rates of 2%-5% in affluent countries and 11% in India. Individuals diagnosed with hypothyroidism need to take medication for the rest of their lives, resulting in significant stress. Therefore, conducting a study in this area is imperative., Objective: This study aims to assess the effectiveness of the therapeutic enema (Kshar Basti) and oral Kanchanar Guggul in the treatment of hypothyroidism., Methods: The trial group (n=45) will receive a therapeutic enema (Kshar Basti) followed by oral Ayurvedic drugs for 180 days. The control group (n=45) will be given levothyroxine tablets at a dosage of 1.6 µg/kg/day for the same duration. The objective is to examine the alterations in thyroid stimulating hormone (TSH) levels before and after the treatment., Results: Any deviation of the serum TSH by more than 20% from the initial values, while keeping triiodothyronine (T 3 ), and thyroxine (T 4 ) levels within the normal range, will be deemed statistically significant. Consequently, we anticipate a statistically significant variation in serum TSH levels between the therapeutic enema and Kanchanar Guggul treatments. Presently, the drug preparation operations are in progress. We expect to start enrolling patients in June 2024, do data analysis in December 2025, and acquire results by early 2026, marking the end of this trial., Conclusions: This study will evaluate the efficacy of the therapeutic enema, specifically Kshar Basti, in treating hypothyroidism. Furthermore, more research can determine the efficacy of a therapeutic enema (Kshar Basti) in treating overt hypothyroidism and hypothyroidism during pregnancy., Trial Registration: Clinical Trials Registry India CTRI/2023/05/052389; https://ctri.nic.in/Clinicaltrials/pmaindet2.php?EncHid=Nzk1NjY=&Enc=&userName=052389., International Registered Report Identifier (irrid): PRR1-10.2196/57287., (©Satyajit Pandurang Kulkarni, Shweta Parwe. Originally published in JMIR Research Protocols (https://www.researchprotocols.org), 10.09.2024.)

Background: In this study, we explored the impact of hypothyroidism and thyroid hormone replacement therapy on the risk of developing cardiovascular diseases, including myocardial infarction, heart failure, and cardiac death, via Mendelian randomization analysis., Methods: Genetic instrumental variables related to hypothyroidism, levothyroxine treatment (refer to Participants were taking the medication levothyroxine sodium) and adverse cardiovascular events were obtained from a large publicly available genome-wide association study. Two-sample Mendelian randomization analysis was performed via inverse-variance weighting as the primary method. To ensure the reliability of our findings, we performed MR‒Egger regression, Cochran's Q statistic, and leave-one-out analysis. Additionally, multivariable Mendelian randomization was employed to regulate confounding factors, including systolic blood pressure (SBP), diastolic blood pressure (DBP), body mass index (BMI), diabetes, cholesterol, low-density lipoprotein (LDL), triglycerides and metformin. A mediation analysis was conducted to assess the mediating effects on the association between exposure and outcome by treating atrial fibrillation and stroke as mediator variables of levothyroxine treatment and bradycardia as mediator variables of hypothyroidism., Results: Genetically predicted hypothyroidism and levothyroxine treatment were significantly associated with the risk of experiencing myocardial infarction [levothyroxine: odds ratio (OR) 3.75, 95% confidence interval (CI): 1.80-7.80; hypothyroidism: OR: 15.11, 95% CI: 2.93-77.88]. Levothyroxine treatment was also significantly related to the risk of experiencing heart failure (OR: 2.16, 95% CI: 1.21-3.88). However, no associations were detected between hypothyroidism and the risk of experiencing heart failure or between hypothyroidism or levothyroxine treatment and the risk of experiencing cardiac death. After adjusting for confounding factors, the results remained stable. Additionally, mediation analysis indicated that atrial fibrillation and stroke may serve as potential mediators in the relationships between levothyroxine treatment and the risk of experiencing heart failure or myocardial infarction., Conclusion: The results of our study suggest a positive association between hypothyroidism and myocardial infarction and highlight the potential effects of levothyroxine treatment, the main thyroid hormone replacement therapy approach, on increasing the risk of experiencing myocardial infarction and heart failure., (© 2024. The Author(s).)

Refractory hypothyroidism (RF) defined as raised serum levels of thyroid stimulating hormone (TSH) above upper limit of the reference range with or without the persistence of hypothyroid symptoms following a 6-week interval after the dosage was last increased to upper limits of dose per age. The most common cause of RH is inadequate compliance. In addition, diet, concomitant medication interactions, and gastrointestinal diseases can all result in l-thyroxine (LT4) malabsorption, which can cause RH. Moreover, weight gain, switching brands of LT4, poor storage of LT4, chronic liver disorders, cystic fibrosis, nephrotic syndrome, consumptive hypothyroidism, Addison's disease are significant contributors to RF in children. RH in children is frequently asymptomatic, when symptoms do occur, they are typically minor and resemble those of hypothyroidism. It is essential to identify RH early and treat its underlying cause in order to avoid overusing LT4, which can lead to cardiac and bone problems. Endocrinologists should handle children who they suspect of having RH methodically after making sure there is enough compliance. Searching for undiagnosed illnesses and/or other factors that can affect LT4 absorption could be part of this. We present this review after an extensive literature search and long-standing clinical experience. This review's objective is to shed light on the causes, clinical manifestations, investigations, and treatment of RH in children., (© 2024 Walter de Gruyter GmbH, Berlin/Boston.)

Amiodarone is an antiarrhythmic drug which may be associated with thyroid dysfunction. Type I amiodarone-induced thyrotoxicosis (AIT) is treated with thionamides and type II AIT is treated with glucocorticoids. Combined therapy is used in mixed or indeterminate forms. When medical treatment is unsuccessful, radioiodine ablation or thyroidectomy is considered. This report reviews a case of AIT refractory to conventional treatment. Despite high doses of methimazole and prednisone, the patient remained clinically and biochemically thyrotoxic. Cholestyramine, a bile salt sequestrant, was used as an off-label adjunctive treatment resulting in significant improvement and achievement of euthyroidism that may also be in part due to the expected natural timeline of recovery from AIT after several months. The patient subsequently trended towards hypothyroidism with symptomatic weight gain and cold intolerance for which he was initiated on levothyroxine., Competing Interests: Competing interests: None declared., (© BMJ Publishing Group Limited 2024. No commercial re-use. See rights and permissions. Published by BMJ.)

Objective: The aim of this study is to assess the impact of extrathyroidal autoimmune diseases (ADs) on the clinical characteristics and efficacy of iodine-131 ( 131 I) therapy in patients with differentiated thyroid cancer (DTC)., Methods: Patients with DTC who were received 131 I therapy simultaneously were classified into the combination group (n = 35) and noncombination group (n = 146) depending on the presence of ADs. The clinical characteristics, such as gender, age, tumor lesions, lymph node metastasis, distant metastasis, 131 I therapy efficacy, and use of levothyroxine, were compared between the two groups. Statistical analysis was conducted using SPSS 26.0 and R 4.0.3., Results: There was a statistically significant difference in age between the combination and noncombination groups (t = -2.872, p < .01), and the optimal cutoff value was 50.5 years. Propensity score matching was completed effectively on a total of 121 patients, using age as the matching factor, comprising 32 cases in the combination group and 80 cases in the noncombination group. The baseline demographic features of the two groups were equivalent after matching (p > .05), and there was no significant difference in the therapeutic efficacy of 131 I between the two groups (p > .05). In the subgroup analysis involving patients aged great than 50.5 years, the levothyroxine/weight (µg/kg) was increased in the combination group, and the difference was statistically significant (p < .05)., Conclusion: While extrathyroidal ADs may enhance the detection of DTC among elderly women, they have no impact on the clinical characteristics of thyroid cancer or the efficacy of 131 I therapy. ADs may necessitate higher per-unit dosages of levothyroxine in patients with DTC, regardless of the clinical status. Consequently, it is not essential for nuclear medicine physicians to consider the presence of ADs when designing treatment plans for patients with DTC., (© 2024 The Author(s). Immunity, Inflammation and Disease published by John Wiley & Sons Ltd.)

A 28-year-old woman presented with a 4-year history of fatigue and sleepiness and was found to have central hypothyroidism and mood disorder. The patient had normal thyroid volume and did not show any other pituitary axis involvement. Over the course of the disease, her symptom improvement matched with the free thyroxine (FT 4 ) rebound and the adjustment of antipsychotic medication. The patient's grandmother had central hypothyroidism, and her mother and uncle had lowered or inappropriately normal thyroid stimulating hormone. Hence, genetic involvement was highly suspected, but whole exon sequencing did not reveal a pathogenic variant. Levothyroxine tablets were prescribed to maintain a normal median level of FT 4 , and mood disorder medications were adjusted by specialists. Isolated central hypothyroidism is extremely rare, and we report this case aiming to raise awareness of this condition.

Levothyroxine is one of the most prescribed drugs in the western world. Dosing is challenging due to high-interindividual differences in effective dosage and the narrow therapeutic window. Model-informed precision dosing (MIPD) using machine learning could assist general practitioners (GPs), but no such models exist for primary care. Furthermore, introduction of decision-support algorithms in healthcare is limited due to the substantial gap between developers and clinicians' perspectives. We report the development, validation, and a clinical simulation trial of the first MIPD application for primary care. Stable maintenance dosage of levothyroxine was the model target. The multiclass model generates predictions for individual patients, for different dosing classes. Random forest was trained and tested on a national primary care database (n = 19,004) with a final weighted AUC across dosing options of 0.71, even in subclinical hypothyroidism. TSH, fT4, weight, and age were most predictive. To assess the safety, feasibility, and clinical impact of MIPD for levothyroxine, we performed clinical simulation studies in GPs and compared MIPD to traditional prescription. Fifty-one GPs selected starting dosages for 20 primary hypothyroidism cases without and then with MIPD 2 weeks later. Overdosage and underdosage were defined as higher and lower than 12.5 μg relative to stable maintenance dosage. MIPD decreased overdosage in number (30.5 to 23.9%, P < 0.01) and magnitude (median 50 to 37.5 μg, P < 0.01) and increased optimal starting dosages (18.3 to 30.2%, P < 0.01). GPs considered lab results more often with MIPD and most would use the model frequently. This study demonstrates the clinical relevance, safety, and effectiveness of MIPD for levothyroxine in primary care., (© 2024 The Authors. Clinical Pharmacology & Therapeutics published by Wiley Periodicals LLC on behalf of American Society for Clinical Pharmacology and Therapeutics.)

Background: Obesity and hypothyroidism are common medical conditions that are associated with each other. Bariatric surgery (BS) is a common approach used to achieve substantial weight loss in obese patients. However, there is limited evidence regarding the need for postsurgery levothyroxine (LT4) dose adjustment in patients with hypothyroidism undergoing BS. Methods: This was a three-year prospective cohort study assessing postsurgery LT4 requirements with attention to body composition changes. The current study included 1030 patients with hypothyroidism, who underwent sleeve gastrectomy (SG) ( n = 707, 88.3% women) or one anastomosis gastric bypass (OAGB) ( n = 323, 92% women). Patients were followed for 36 months after surgery. A bioelectrical impedance analyzer was used for body composition assessment. LT4 requirements were assessed by generalized estimating equation (GEE) methods adjusted for weight as a time-varying covariate. Results: During the follow-up, TSH (mIU/L) and T4 (ng/dL) measurements did not significantly change in the OAGB group over time. However, in the SG group, TSH measurement decreased over time ( p trend = <0.001). In the third year of the follow-up, 56.1% and 33.3% of patients in the SG and OAGB groups experienced LT4 (μg/day) dose reduction, while 24.4% and 9.1% of the participants experienced LT4 dose increments, respectively. GEE analysis showed a significant increase in the LT4/fat mass (FM) (μg/kg) ratio after 36 months of follow-up compared with the baseline in both the SG [1.8 (1.5-2.2) to 2.7 (2.0-3.5), p trend = 0.039)] and OAGB [1.7 (1.4-2.2) to 3.2 (2.7-4.8), p trend = <0.001)] groups. Moreover, patients who underwent OAGB experienced greater LT4/FM (μg/kg) dose adjustments compared to those undergoing SG ( p between = 0.060). In both groups, after the first year, the increase in LT4/FM (μg/kg) plateaued ( p interaction = 0.009). Conclusion: Most hypothyroid patients experienced either a reduction or no change in LT4 (μg/day) dosage after 36 months in both surgical groups. The LT4/FM (μg/kg) was significantly increased in patients undergoing either SG or OAGB with greater alterations in the latter. Further studies on larger populations and with longer duration of follow-up are needed to confirm our results.

Subclinical hypothyroidism and thyroid autoimmunity in pregnancy are common conditions. They are both associated with adverse maternal and offspring outcomes. Women with thyroid autoimmunity should be monitored with regular thyroid function tests preconception and during gestation to identify women who develop hypothyroidism. The effectiveness of thyroid hormone treatment in reducing adverse outcomes in pregnancy has been studied in a number of randomized controlled trials. Current evidence shows obstetrical benefits of levothyroxine treatment in pregnant women with a thyroid-stimulating hormone level greater than 4 mU/L., Competing Interests: Disclosure The authors have nothing to disclose., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Objective: The aim of this study is to investigate the relationship between the use of high doses of levothyroxine (L-T4) and hearing loss in patients who have undergone surgery for thyroid cancer., Material Method: After total thyroidectomy for thyroid cancer, patients were divided into two groups according to L-T4 dose below 150 µg and above 150 µg. Demographic characteristics, postoperative duration, radioactive iodine treatment, bone densitometry scans with LDxa and FDxa, and right and left ear hearing levels were statistically compared in both groups., Results: The study included 62 patients, 85.5% (n = 53) of whom were female, with a mean age of 48.8 ± 11.7 years. While 56.45% (n = 35) of the patients were taking L-T4 below 150 µg 43.55% (n = 27) were taking L-T4 above 150 µg. The mean postoperative duration of the participants was 4.1 ± 2.7 years, osteopenic 30.7% and osteoporotic 16.13% according to LDxa, osteopenic 29.0% and osteoporotic 1.6% according to FDxa. Hearing loss in both right and left ears was 41.9% and sensorineural hearing loss in both ears was 22.6%. Age, LDxa, FDxa, hearing loss in the right and left ear were found to be significantly different in the two groups above and below 150 µg according to the dose of L-T4 used (p < 0.05). However, no differences were found according to sex, height, weight, body mass index, postoperative period, or radioactive iodine treatment (p > 0.05). Both osteopenia and osteoporosis, as well as hearing loss in both the right and left ear, were significantly higher in the group taking L-T4 150 µg or more (p < 0.05)., Conclusion: In our study, we found that patients taking 150 µg or more of L-T4 daily were more osteopenic and osteoporotic and had more hearing loss in both ears., Competing Interests: Declarations Conflicts of interest All authors certify that they have no affiliation or involvement with any organisation or entity that has any financial or non-financial interest in the subject matter or materials discussed in this manuscript. Ethical approval All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. Informed consent Informed consent was obtained from all individual participants included in the study., (© 2024. The Author(s).)

Objective: To study school achievement in grade 9 of compulsory school in children with congenital hypothyroidism (CH), both those detected by the national screening program and those with a normal screening result and thus diagnosed later., Study Design: Nationwide study of children in the Swedish Medical Birth Register (n = 1 547 927) from 1982 through 1997, linked to the neonatal screening CH cohort and the National School Register. Dried blood spot (DBS) samples are collected from all newborn infants, according to the neonatal screening program. Thyroid-stimulating hormone was used for CH screening. CH was defined as either having an abnormal screening result (DBS+) and treatment with levothyroxine (LT4+) or having a normal screening result but a CH diagnosis in the National Patient Register and treatment with LT4 (DBS-/ICD+/LT4+). Regression models were used to study school performance, which as measured as grade point sum and national test results. Sibling analysis also was performed to account for unmeasured familial factors., Results: There were 448 children who were DBS+/LT4+ and 475 children who were DBS-/ICD+/LT4+. Children with CH had lower grade point sum, adjusted β = - 6.34 (95% CI -11.7 to -1.01) and adjusted β = -10.3 (95% CI -15.5 to -5.20) for those with abnormal (DBS+/LT4+) and normal screening (DBS-/ICD+/LT4+) results, respectively. CH also was associated with lower result on the national tests, especially in mathematics. These associations remained in the sibling analyses., Conclusions: Youth with CH had slightly lower school achievements compared with those without CH and compared with their siblings. CH children with a normal screening result, and thus diagnosed later, presented the lowest results on grade point sum and national tests., Competing Interests: Declaration of Competing Interest A.G. was supported by Region Stockholm (clinical post doctorial appointment). Financial support also was provided from the Swedish Research Council through the Swedish Initiative for Research on Microdata in the Social and Medical Sciences (SIMSAM) framework grant no 340-2013-5867,Sällskapet Barnavård, Karolinska Institutetand The Samariten Foundation for paediatric research. The authors declare they have no actual or potential competing financial interests., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Regardless of the cause, hypothyroidism should be treated with levothyroxine. The objectives of management are the normalization of TSH levels and the relief of symptoms. In general, the vast majority of patients who achieve normalization of TSH levels show a resolution of symptoms; however, for a small number of individuals, symptoms persist (despite adequate control of TSH). This scenario generates a dilemma in the therapeutic approach to these patients, because even when excluding other causes or concomitant diseases that can explain the persistence of symptoms, pharmacological management strategies are scarce. Consequently, the efficacy of some less conventional approaches to therapy, such as the use of LT3 monotherapy, desiccated thyroid extracts, and LT4/LT3 combinations, in addressing persistent hypothyroid symptoms have been evaluated in multiple studies. The majority of these studies did not observe a significant benefit from these "nonconventional" therapies in comparison to results with LT4 monotherapy alone. Nevertheless, some studies report that a significant proportion of patients prefer an alternative to monotherapy with LT4. The most common approach has been to prescribe a combination of LT4 and LT3, and this review describes and analyzes the current evidence of the efficacy of LT4/LT3 combination therapy vs. LT4 monotherapy in addressing persistent hypothyroidism symptoms to provide suggested guidelines for clinicians in the management of these patients.

Purpose: To develop a predictive model using machine learning for levothyroxine (L-T4) dose selection in patients with differentiated thyroid cancer (DTC) after resection and radioactive iodine (RAI) therapy and to prospectively validate the accuracy of the model in two institutions., Methods: A total of 266 DTC patients who received RAI therapy after thyroidectomy and achieved target thyroid stimulating hormone (TSH) level were included in this retrospective study. Sixteen clinical and biochemical characteristics that could potentially influence the L-T4 dose were collected; Significant features correlated with L-T4 dose were selected using machine learning random forest method, and a total of eight regression models were established to assess their performance in prediction of L-T4 dose after RAI therapy; The optimal model was validated through a two-center prospective study (n=263)., Results: Six significant clinical and biochemical features were selected, including body surface area (BSA), weight, hemoglobin (HB), height, body mass index (BMI), and age. Cross-validation showed that the support vector regression (SVR) model was with the highest accuracy (53.4%) for prediction of L-T4 dose among the established eight models. In the two-center prospective validation study, a total of 263 patients were included. The TSH targeting rate based on constructed SVR model were dramatically higher than that based on empirical administration (Rate 1 (first rate): 52.09% (137/263) vs 10.53% (28/266); Rate 2 (cumulative rate): 85.55% (225/263) vs 53.38% (142/266)). Furthermore, the model significantly shortens the time (days) to achieve target TSH level (62.61 ± 58.78 vs 115.50 ± 71.40)., Conclusions: The constructed SVR model can effectively predict the L-T4 dose for postoperative DTC after RAI therapy, thus shortening the time to achieve TSH target level and improving the quality of life for DTC patients., Competing Interests: The authors declare that financial support was received for the research, authorship, and/or publication of this article., (Copyright © 2024 Liu, Wang, Yue, Yin, Tong, Fu, Ma, Li, Liu, Zhang, Su, Yang, Li, Xu and Dai.)

We report a woman in her 30s with dysferlinopathy whose diagnosis was masked by superimposed hypothyroidism. Laboratory studies revealed Hashimoto's thyroiditis and markedly raised serum creatine kinase (CK of 6255 U/L; reference range 0-170 U/L). Electromyography, nerve conduction studies and MRI of the hip and thigh were consistent with a diagnosis of hypothyroid myopathy, but thyroxine failed to resolve her clinical presentation or normalise the CK level. Immunohistochemical (IHC) staining of right vastus lateralis muscle biopsy revealed the selective absence of dysferlin leading to a diagnosis of limb-girdle muscular dystrophy type IIB. Dysferlinopathy is a challenging diagnosis due to a varied clinical picture and low incidence. Misdiagnosis is common even in uncomplicated presentations, and this case outlines the need for routine inclusion of IHC and a low threshold for genetic testing, in the workup of complex myopathy., Competing Interests: Competing interests: None declared., (© BMJ Publishing Group Limited 2024. No commercial re-use. See rights and permissions. Published by BMJ.)

Rationale: This study reports the first case of congenital hypothyroidism (CH) and alpha thalassemia in a child in China, with anemia and muscle damage as the main manifestations. Analyzing and studying this case is of great significance in reducing missed and misdiagnosed CH and will provide a clinical strategy for treating these patients., Patient Concerns: Child, female, 2 years and 7 months old, the child appeared dispirited, had poor appetite, shallow complexion, reduced activities with anemia, elevated muscle enzymes, height, and growth retardation., Diagnoses: The child was diagnosed with CH with alpha thalassemia., Interventions: The patient was treated with levothyroxine sodium and anemia correction., Outcomes: The children's current spirit, appetite, red face, normal limb activity, physical development, and intelligence were significantly better than those of normal children of the same age., Conclusions: CH with alpha thalassemia, especially anemia and muscle damage as the main manifestations, has not been reported. Administration of levothyroxine sodium is effective in correcting anemia in patients with CH and alpha thalassemia., Lesson: Due to CH and alpha thalassemia, there are no specific symptoms and they are prone to missed diagnosis and misdiagnosis. Therefore, patients with anemia and elevated muscle enzyme levels should be routinely tested for thyroid function to diagnose them early and provide proper treatment to avoid negative consequences., Competing Interests: The authors have no conflicts of interest to disclose., (Copyright © 2024 the Author(s). Published by Wolters Kluwer Health, Inc.)

Objective: Levothyroxine (LT 4 ) monotherapy is the current recommended approach for treating pediatric patients post-total thyroidectomy (TT) based on the assumption that peripheral conversion of thyroxine (T 4 ) to triiodothyronine (T 3 ) normalizes thyroid hormone levels. In adults, approximately 15% of post-TT patients on LT4 monotherapy have altered T 4 :T 3 ratios with ongoing debate in regard to the clinical impact with respect to health-related quality of life (hrQOL). The ability to normalize T 3 and T 4 levels on LT 4 monotherapy for pediatric patients' post-TT is important but not previously described. This study reports data on T 3 levels in athyreotic pediatric patients to determine if a similar cohort of patients exists on LT4 monotherapy targeting normalization of TSH (LT4 replacement) or suppression (LT4 suppression)., Methods: Thyroid function tests (TFTs) were retrospectively extracted from medical charts for patients <19 years old who underwent TT for definitive treatment of Graves' disease (GD) or differentiated thyroid cancer (DTC) between 2010-2021. LT4 dosing was selected to normalize the TSH in GD patients (LT4 replacement) or suppress TSH in DTC patients (LT4 suppression). Pre- and post-surgical TSH, T3 and T4 levels were compared., Results: Of 108 patients on LT 4 replacement (n=53) or LT 4 suppression (n=55) therapy, 94% (102/108) of patients demonstrated T 3 levels in the normal range post-TT. However, the majority of patients on LT 4 replacement (44/53; 83%) and LT 4 suppression (31/55; 56%) displayed post-TT T 3 levels in the lower half of the normal range despite 50% (22/44) and 48% (15/31) of these patients, respectively, having post-TT fT 4 levels above the upper limit of the normal range., Conclusion: A significant number of pediatric patients do not achieve similar T 3 and T 4 :T 3 levels pre- and post-TT. Future multi-center, prospective studies evaluating LT 4 monotherapy in comparison to combined LT 4 /LT 3 therapy are warranted to determine the potential clinical impact of altered T3 levels in athyreotic pediatric patients., Competing Interests: AB is a consultant for IBSA Pharm and Rare Thyroid Therapeutics/Egetis Therapeutics. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Baran, Isaza, Bojarsky, Alzoebie, Song, Halada, Sisko, Gonzales, Mostoufi-Moab and Bauer.)

Rationale: Hashimoto thyroiditis (HT), a common cause of hypothyroidism, has shown an increasing incidence in recent years, particularly among women. In addition to the common complications such as lipid metabolism disorders, patients with HT may also experience some serious complications, acute kidney injury and severe muscle damage for instance. This article explored the effectiveness of levothyroxine sodium tablets (L-T4) replacement therapy in severe complications of hypothyroidism, including treatment dosage, duration of complication recovery, and whether additional treatment is needed., Patient Concerns, Diagnoses, and Interventions: We described a case of a 52-year-old woman with HT who exhibited kidney injury, muscle injury, and lipid metabolism disorders. The increased levels of serum creatinine, creatine kinase, cholesterol, triglyceride, low density lipoprotein cholesterol, high density lipoprotein cholesterol, and the decreased levels of estimated glomerular filtration rate were obviously observed. This patient was started on L-T4 (75 and 100 µg, alternate)., Outcomes and Lessons: Following a two-month treatment, the serum creatine kinase level decreased to within normal range. The estimated glomerular filtration rate level was restored, and the serum creatinine level was down-regulated, although slightly higher than the normal range. L-T4 partially reversed HT-induced the disorders of muscle, renal function, and lipid profile of this patient and remarkably alleviated her HT-related symptoms., Competing Interests: The authors have no conflicts of interest to disclose., (Copyright © 2024 the Author(s). Published by Wolters Kluwer Health, Inc.)

Objective: Thyroid hormones are known to affect the biosynthesis and degradation of antioxidant compounds, suggesting a possible link between hypothyroidism and oxidative stress. However, there is no clear consensus in the literature regarding this association. The aim of this study was to evaluate oxidative stress markers (extracellular thiol-disulfide homeostasis and intracellular glutathione homeostasis) in patients with hypothyroidism due to autoimmune (Hashimoto's thyroiditis) or nonautoimmune thyroid disease rendered euthyroid after levothyroxine replacement., Subjects and Methods: The study included 116 patients admitted to the Taksim Training and Research Hospital (Istanbul, Türkiye). Of these, 50 had hypothyroidism due to Hashimoto's thyroiditis (HT group), 30 had nonautoimmune hypothyroidism (NAIH group), and 36 were healthy controls (control group). All participants were women. Extracellular thiol-disulfide homeostasis and intracellular glutathione homeostasis tests were assessed as oxidative stress markers., Results: Thiol-disulfide homeostasis in both HT and NAIH groups was shifted toward the oxidative spectrum. Compared with the control group, the HT and NAIH groups had lower levels of native (p < 0.001 and p = 0.001, respectively) and total (p = 0.002 and p = 0.012, respectively) thiol, as well as a lower native thiol/total thiol ratio (p < 0.001 for both). The HT group also had higher disulfide levels than the control group (p = 0.027). Reduced glutathione (GSH) and oxidized glutathione (GSSG) values were comparable across all three groups, but the HT and NAIH groups had higher GSSG/GSH (p < 0.001 for both) and GSSG/(GSH+GSSG) ratios (p = 0.003 and p = 0.005, respectively), along with lower GSH/(GSH+GSSG) ratio (p = 0.001 and p = 0.002, respectively) than the control group., Conclusion: Levothyroxine replacement was ineffective in ameliorating oxidative stress in patients with hypothyroidism due to Hashimoto's thyroiditis or nonautoimmune causes, as extracellular thiol-disulfide homeostasis was notably altered in these patients compared with healthy controls. The findings of this study suggest that oxidative stress remains a prevailing issue in patients with autoimmune or nonautoimmune hypothyroidism even after euthyroidism is restored., Competing Interests: Disclosure: no potential conflict of interest relevant to this article was reported.

Biallelic loss-of-function variants in the IYD gene cause hypothyroidism resulting from iodine wasting. We describe 8 patients (from 4 families in which the parents are first cousins) who are homozygous for a variant in IYD (including a novel missense deleterious variant, c.791C>T [P264L], in 1 family). Seven patients presented between 5 and 16 years of age with a large goiter, overt hypothyroidism, and a high serum thyroglobulin. The goiter subsided with levothyroxine therapy in most. Upon stopping levothyroxine in 5 patients, goiter and hypothyroidism reappeared in 3. In these 3 patients, a rising serum thyroglobulin concentration preceded hypothyroidism and goiter and urinary iodine excretion was low. In patients who remained euthyroid, urinary iodine was normal. In conclusion, these patients bearing biallelic pathogenic variants in IYD developed a large goiter, a high serum thyroglobulin, and overt hypothyroidism when their iodine intake was low., Competing Interests: Conflict of interest: C.H., N.D., and C.B. are members of the MTG-8 Study Group of the European Reference Network for Rare Endocrine Disease, Endo-ERN., (© The Author(s) 2024. Published by Oxford University Press on behalf of European Society of Endocrinology. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.)

Context: Several endocrine abnormalities were reported in children with Prader-Willi syndrome (PWS), including hypothyroidism. Growth hormone (GH) treatment may impact the thyroid hormone axis by direct inhibition of T4 or TSH secretion or by increased peripheral conversion of free T4 (FT4) to T3., Objective: The objective of this study is to evaluate thyroid function during GH treatment in a large group of children with PWS., Methods: Serum FT4, T3, and TSH are measured in a 2-year randomized controlled GH trial (RCT) and 10-year longitudinal GH study (GH treatment with 1.0 mg/m²/day [∼0.035 mg/kg/day])., Results: Forty-nine children with PWS were included in the 2-year RCT (median [interquartile range, IQR] age: GH group 7.44 [5.47-11.80] years, control group 6.04 [4.56-7.39] years). During the first 6 months, median (IQR) FT4 standard deviation score (SDS) decreased in the GH group from -0.84 (-1.07 to -0.62) to -1.32 (-1.57 to -1.08) (P < .001) and T3 SDS increased from 0.31 (-0.01-0.63) to 0.56 (0.32-0.79) (P = .08), while in the control group, FT4 and T3 SDS remained unchanged. In our 10-year GH study, 240 children with PWS (median [IQR] age: 1.27 (0.54-4.17) years] were included. Between 2 and 10 years, median (IQR) FT4 SDS remained unchanged, being -0.87 (-0.98 to -0.77) after 2 years and -0.88 (-1.03 to -0.74) after 10 years (P = .13). TSH SDS decreased from -0.35 (-0.50 to -0.21) after 2 years to -0.68 (-0.84 to -0.53) after 10 years (P < .001)., Conclusions: Our findings suggest that GH treatment decreases FT4 levels, due to increased peripheral conversion of FT4 to T3 in the first months of treatment, but thereafter, FT4 and T3 normalize and remain stable during long-term GH treatment in almost all children and adolescents with PWS., (© The Author(s) 2024. Published by Oxford University Press on behalf of European Society of Endocrinology.)

Background: Lugol solution is often administered to patients with Graves' disease before surgery. The aim is to reduce thyroid vascularization and surgical morbidity, but its real effectiveness remains controversial. The present study was designed to evaluate the effects of preoperative Lugol solution on thyroid vascularization and surgical morbidity in patients with Graves' disease undergoing total thyroidectomy., Methods: Fifty-six patients undergoing total thyroidectomy for Graves' disease were randomly assigned to receive 7 days of Lugol treatment (Lugol+ group, 29) or no Lugol treatment (LS- group, 27) before surgery in this single-centre and single-blinded trial. Preoperative hormone and colour Doppler ultrasonographic data for assessing thyroid vascularization were collected 8 days before surgery (T0) and on the day of surgery (T1). The primary outcome was intraoperative and postoperative blood loss. Secondary outcomes included duration of surgery, thyroid function, morbidity, vascularization, and microvessel density at final pathology., Results: No differences in demographic, preoperative hormone or ultrasonographic data were found between LS+ and LS- groups at T0. At T1, free tri-iodothyronine (FT3) and free thyroxine (FT4) levels were significantly reduced compared with T0 values in the LS+ group, whereas no such variation was observed in the LS- group. No differences between T0 and T1 were found for ultrasonographic vascularization in either group, nor did the histological findings differ. There were no significant differences between the LS+ and LS- groups concerning intraoperative/postoperative blood loss (median 80.5 versus 94 ml respectively), duration of surgery (75 min in both groups) or postoperative morbidity., Conclusion: Lugol solution significantly reduces FT3 and FT4 levels in patients undergoing surgery for Graves' disease, but does not decrease intraoperative/postoperative blood loss, thyroid vascularization, duration of surgery or postoperative morbidity., Registration Number: NCT05784792 (https://www.clinicaltrials.gov)., (© The Author(s) 2024. Published by Oxford University Press on behalf of BJS Foundation Ltd. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.)

This case report presents the clinical course and management of a 62-year-old female patient with atrial fibrillation (AF) secondary to levothyroxine overdose along with an underlying secondary infection. The patient was admitted with sudden onset dyspnea, altered sensorium, and neurological deficits. Upon examination, she exhibited tachycardia, irregular heart sounds, and extensive crepitations in the respiratory system. Her electrocardiogram (ECG) showed an absent P wave with a varying RR interval. Laboratory investigations revealed abnormal thyroid function tests (TFTs) and raised polymorphonuclear cells, in addition to hyperglycemia. The patient was managed in the intensive care unit (ICU) with bilevel positive airway pressure (BiPAP) and supplemental oxygen, treated for AF with intravenous (IV) amiodarone, and her blood sugar was controlled with insulin infusion. Discontinuation of levothyroxine therapy was advised. Subsequently, her AF was terminated, and sinus rhythm was restored. Her neurological examination showed right-sided hemiplegia with aphasia. After 1 week of treatment, her TFTs normalized, and she was discharged on appropriate medication., (© Journal of the Association of Physicians of India 2024.)

Objectives: The use of levothyroxine (LT4) treatment aiming to improve fertility in euthyroid women with positive thyroid peroxidase antibodies (TPOAb) is not supported by the available evidence. The aim of the study was to document the use of LT4 by European thyroid specialists in such patients., Design: The data presented derive from Treatment of Hypothyroidism in Europe by Specialists, an International Survey (THESIS), a questionnaire conducted between 2019 and 2021 to document the management of hypothyroidism by European thyroid specialists. Here, we report the aggregate results on the use of LT4 in infertile, euthyroid women with positive TPOAb., Results: A total of 2316/5406 (42.8%) respondents stated that LT4 may be indicated in TPOAb positive euthyroid women with infertility. The proportion of those replying positively to this question varied widely across different countries (median 39.4, range 22.9%-83.7%). In multivariate analyses males (OR: 0.8; CI: 0.7-0.9) and respondents >60 years (OR: 0.7; 0.6-0.8) were the least inclined to consider LT4 for this indication. Conversely, respondents managing many thyroid patients ("weekly" [OR: 1.4; CI: 1.0-1.9], "daily" [OR: 1.8; CI: 1.3-2.4]) and practicing in Eastern Europe (OR: 1.5; CI: 1.3-1.9) were most likely to consider LT4., Conclusions: A remarkably high number of respondents surveyed between 2019 and 2021, would consider LT4 treatment in TPOAb positive euthyroid women with infertility. This view varied widely across countries and correlated with sex, age and workload, potentially influencing patient management. These results raise concerns about potential risks of overtreatment., (© 2024 John Wiley & Sons Ltd.)

Backgruound: The adequate dose of levothyroxine (LT4) for patients who have undergone total thyroidectomy (TT) for differentiated thyroid cancer (DTC) is uncertain. We evaluated the LT4 dose required to achieve mild thyroid-stimulating hormone (TSH) suppression in DTC patients after TT., Methods: The electronic medical records of patients who underwent TT for DTC and received mild TSH suppression therapy were reviewed. Linear regression analysis was performed to evaluate the association between LT4 dose (μg/kg) and an ordinal group divided by body mass index (BMI). We also evaluated the trend in LT4 doses among groups divided by BMI and age., Results: In total, 123 patients achieved mild TSH suppression (0.1 to 0.5 mIU/L). The BMI variable was divided into three categories: <23 kg/m2 (n=46), ≥23 and <25 kg/m2 (n=30), and ≥25 kg/m2 (n=47). In the linear regression analysis, BMI was negatively associated with the LT4 dose after adjusting for age and sex (P<0.001). The LT4 doses required to achieve mild TSH suppression based on the BMI categories were 1.86, 1.71, and 1.71 μg/kg, respectively (P for trend <0.001). Further analysis with groups divided by age and BMI revealed that a higher BMI was related to a lower LT4 dose, especially in younger patients aged 20 to 39 (P for trend=0.011)., Conclusion: The study results suggest an appropriate LT4 dose for mild TSH suppression after TT based on body weight in patients with DTC. Considering body weight, BMI, and age in estimating LT4 doses might help to achieve the target TSH level promptly.

Background: While the benefits of levothyroxine are well-established for overt hypothyroidism, they are unclear for subclinical hypothyroidism (SCH) among pregnant women., Objective: To estimate the effect of initiation of levothyroxine on pregnancy loss among women with SCH with an emulated target trial using observational data., Methods: We emulated a target trial using the United Kingdom's Clinical Practice Research Datalink to account for the staggered timing of diagnosis and treatment of SCH and the time of entry of women into prenatal care. We emulated multiple nested trials (at each gestational week) and used an intention-to-treat approach to define levothyroxine use (≥1 prescription in the 7 days prior to trial entry), with eligible users matched to non-users (1:4) on time of diagnosis, gestational week of the first eligible trial and high-dimensional propensity score. Pregnancy losses included spontaneous abortion and stillbirth. A pooled logistic regression model with bootstrap resampling was used to estimate the hazard ratios (HR) and 95% confidence intervals (CI)., Results: Based on 159,177 eligible person-trials (5781 women), the matched cohort included 181 initiators and 640 non-initiators of levothyroxine, with 57 pregnancy losses occurring during follow-up. Overall, the mean age of women was 32.2 years (SD 5.4), 25% were obese, 8% had type 2 diabetes and about 50% were nulliparous. After matching, women who initiated levothyroxine versus not had higher thyroid-stimulating levels during pregnancy and were more likely to have a history of hypothyroidism. The cumulative incidence of pregnancy loss was lower in initiators versus non-initiators of levothyroxine. The adjusted HR for pregnancy loss was 0.87 (95% CI 0.22, 1.56)., Conclusions: Although our assessment of the effect of initiation of levothyroxine for SCH in pregnancy precludes any definitive conclusions due to wide confidence intervals, this study illustrates the feasibility of using the target trial emulation framework to examine the effectiveness of medication use in pregnancy., (© 2023 The Authors. Paediatric and Perinatal Epidemiology published by John Wiley & Sons Ltd.)

Purpose: Gestational weight gain (GWG) is an important contributor to pregnancy outcomes in the general obstetric population and different subgroups. The corresponding information in women with thyroid conditions is limited. We aimed to evaluate the relationship between GWG according to institute of medicine (IOM) and pregnancy outcomes in women with thyroid disorders., Methods: We performed a retrospective analysis of 620 pregnant women either treated with levothyroxine (N = 545) or attended because of hyperthyroidism during pregnancy (N = 75)., Results: The associations between GWG according to IOM and pregnancy outcomes were present both in women treated with thyroid hormone and women followed by hyperthyroidism, most of them related to the fetal outcomes. In women treated with levothyroxine, insufficient GWG was associated with gestational diabetes mellitus (GDM) (odds ratio (OR) 2.32, 95% confidence interval (CI) 1.18, 4.54), preterm birth (OR 2.31, 95% CI 1.22, 4.36), small-for-gestational age newborns (OR 2.38, 95% CI 1.09, 5.22) and respiratory distress (OR 6.89, 95% CI 1.46, 32.52). Excessive GWG was associated with cesarean delivery (OR 1.66, 95% CI 1.10, 2.51) and macrosomia (OR 2.75, 95% CI 1.38, 5.49). Large-for-gestational age newborns were associated with both insufficient GWG (OR 0.25, 95% CI 0.11, 0.58) and excessive GWG (OR 1.80, 95% CI 1.11, 2.92). In women followed by hyperthyroidism, excessive GWG was associated with large-for-gestational age newborns (OR 5.56, 95% CI 1.03, 29.96)., Conclusion: GWG according to IOM is associated with pregnancy outcomes both in women treated with thyroid hormone and women followed by hyperthyroidism., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)