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Both hyperthyroidism and hypothyroidism can have adverse effects in pregnancy. The most common causes of thyrotoxicosis in pregnancy are gestational transient thyrotoxicosis and Graves' disease. It is important to distinguish between these entities as treatment options differ. Women of reproductive age who are diagnosed with Graves' disease should be counseled regarding the impact of treatment options on a potential pregnancy. Although the absolute risk is small, antithyroid medications can have teratogenic effects. Propylthiouracil appears to have less severe teratogenicity compared to methimazole and is therefore favored during the first trimester if a medication is needed. Women should be advised to delay pregnancy for at least 6 months following radioactive iodine to minimize potential adverse effects from radiation and ensure normal thyroid hormone levels prior to conception. As thyroid hormone is critical for normal fetal development, hypothyroidism is associated with adverse obstetric and child neurodevelopmental outcomes. Women with overt hypothyroidism should be treated with levothyroxine (LT4) to a thyrotropin (thyroid-stimulating hormone; TSH) goal of <2.5 mIU/L. There is mounting evidence for associations of maternal hypothyroxinemia and subclinical hypothyroidism with pregnancy loss, preterm labor, and lower scores on child cognitive assessment. Although there is minimal risk of LT4 treatment to keep TSH within the pregnancy-specific reference range, treatment of mild maternal thyroid hypofunction remains controversial, given the lack of clinical trials showing improved outcomes with LT4 treatment. [ABSTRACT FROM AUTHOR]

Context: Physiological alterations challenge the assessment of maternal thyroid function in pregnancy. It remains uncertain how the reference ranges vary by week of pregnancy, and how the classification of disease varies by analytical method and type of thyroid function test.Design: Serum samples from Danish pregnant women (n = 6282) were used for the measurement of thyrotropin (TSH), total and free thyroxine (T4), total and free 3,5,3'-triiodothyronine (T3), and T-uptake using "Method A" (Cobas 8000, Roche Diagnostics). TSH and free T4 were also measured using "Method B" (ADVIA Centaur XP, Siemens Healthineers).Main Outcome Measures: Pregnancy week- and method-specific reference ranges were established among thyroid antibody-negative women (n = 4612). The reference ranges were used to classify maternal thyroid function, and results were compared by analytical method and type of thyroid function test.Results: The reference ranges for TSH showed a gradual decrease during pregnancy weeks 4 to 14, a gradual increase was observed for total T4, total T3, and T-uptake, whereas free T4 and free T3 showed less variation. When TSH and free T4 were used, Method A classified 935 (14.9%) with abnormal thyroid function, Method B a total of 903 (14.4%), and the methods agreed on 554 individuals. When TSH and total T4 were used, 947 (15.1%) were classified with abnormal thyroid function, and classifications by either total T4 or free T4 agreed on 584 individuals.Conclusions: Even when pregnancy week- and method-specific reference ranges were established, the classification of maternal thyroid dysfunction varied considerably by analytical method and type of thyroid function test. [ABSTRACT FROM AUTHOR]

The 2017 American Thyroid Association guidelines for the diagnosis and management of thyroid disease during pregnancy and the postpartum were published six years after the previous ones. They provide comprehensive clinical recommendations for the whole spectrum of thyroid diseases, as well as for optimal iodine intake during pregnancy, postpartum, and lactation. The present position statement mainly regards the recommended flow chart for therapeutic decision making in pregnant women being diagnosed with subclinical hypothyroidism. Here, we comment on the major biochemical and clinical situations and the corresponding therapeutic recommendations. In particular, we welcome the critical revision of the thyrotropin (TSH) reference range in pregnancy, and we agree that there is no need to treat thyroid peroxidase antibody–negative women with a serum TSH ranging from 2.5 μIU/mL to the upper limit of the reference range. This recommendation will hopefully reduce the huge proportion of healthy pregnant women in whom, according to the previous guidelines, levothyroxine therapy had to be initiated. On the other hand, we are concerned with the recommendation to only “consider treatment” in thyroid peroxidase antibody–negative pregnant women with a serum TSH ranging from the upper limit of the reference range to 10.0 μIU/mL. This is because thyroid antibodies may be falsely negative during gestation, and serum negative chronic autoimmune thyroiditis is a well-known clinical entity even outside pregnancy. Based on these and other arguments, we recommend treatment with levothyroxine in pregnant women with TSH levels ranging between the upper limit of the reference range and 10.0 μIU/mL independently from their thyroid antibody status. [ABSTRACT FROM AUTHOR]

Adequate thyroid hormone availability is important for an uncomplicated pregnancy and optimal fetal growth and development. Overt thyroid disease is associated with a wide range of adverse obstetric and child development outcomes. An increasing number of studies now indicate that milder forms of thyroid dysfunction are also associated with these adverse pregnancy outcomes. The definitions of both overt and subclinical thyroid dysfunction have changed considerably over the past few years, as new data indicate that the commonly used fixed upper limits of 2.5 mU/l or 3.0 mU/l for thyroid-stimulating hormone (TSH) are too low to define an abnormal thyroid function. Furthermore, some studies now show that the reference ranges are not necessarily the best cut-off for identifying pregnancies at high risk of adverse outcomes. In addition, data suggest that thyroid peroxidase autoantibody positivity and high or low concentrations of human chorionic gonadotropin seem to have a more prominent role in the interpretation of thyroid dysfunction than previously thought. Data on the effects of thyroid disease treatment are lacking, but some studies indicate that clinicians should be aware of the potential for overtreatment with levothyroxine. Here, we put studies from the past decade on reference ranges for TSH, determinants of thyroid dysfunction, risks of adverse outcomes and options for treatment into perspective. In addition, we provide an overview of the current views on thyroid physiology during pregnancy and discuss strategies to identify high-risk individuals who might benefit from levothyroxine treatment. [ABSTRACT FROM AUTHOR]

Background: Thyroid disease is a disorder that affects the thyroid gland. Sometimes the body produces too much or too little thyroid hormone. Thyroid hormones regulate metabolism - the way the body uses energy and affect nearly every organ in the body. Thyroid hormone plays a critical role during pregnancy both in the development of a baby and in maintaining the health of the mother. Aim and objectives: To evaluate the thyroid status in pregnancy in light of controversial data and to project our values and ideas. Materials and methods: The present case control study was conducted on 100 patients (obstetric cases) attended and managed in the Department of Obstetrics and Gynecology attached to Geetanjali Medical College and Hospital, Udaipur. The results of the patients were compared with 100 age matched control females having gynecological problems (with normal thyroid values). Fasting blood sample was investigated for the following parameters: T3 (Triiodothyronine), T4 (Thyroxine), TSH (Thyroid Stimulating Hormone). p-value was calculated by using online student t-test calculator. Result: All the cases of the control group had normal T3 values. Values below normal were noted in one case each of I and III trimester and normal values were noted in 80.27 per cent in I trimester, 54.75 per cent in II and 55.28 per cent in the III trimester. Only 18.30 per cent cases of I trimester had raised values of T3 while same was observed in 44.03 per cent in II and 43.51 per cent in III trimester. Variable values of T4 were observed in various trimesters of pregnancy. Values of T4 were below normal in 2.81 per cent in I, 1.20 per cent in II and 1.14 per cent in the III trimester. On the other hand in II and III trimester T4 values were higher than normal in 6.02 per cent and 40.22 per cent respectively. TSH value below normal (0.27μIU/dl) were observed in 2 cases in I and II trimester each while normal values were noted in most of the cases i.e. 77.45 per cent in I, 71.41 per cent in II and 83.31per cent in III trimester. Fluctuating values of TSH above 4.2 μIU/dl were observed in 19.71per cent in I, 26.18per cent in II and 16.66 per cent in the III trimester. Conclusion: T3 values increased during pregnancy significantly more so in II trimester. T4 values were less during I trimester particularly at par during II trimester and increased during III trimester. Raised TSH values were observed during pregnancy as compared to non-pregnant women. Significant increase was observed during II trimester. [ABSTRACT FROM AUTHOR]

Objective: Debate about the need for universal screening of thyroid dysfunction in pregnancy is ongoing. The present study aimed to compare universal screening with targeted high-risk case findings for early diagnosis of thyroid disorders in Iranian pregnant women. Study design: This cross-sectional prospective study was carried out on 1600 pregnant women in their first trimester. A checklist, including all related risk factors recommended by The American Thyroid Association, was completed for all participants. Serum concentrations of thyroxine (T4), T-uptake, TSH and thyroid peroxidase antibody (TPOAb) were measured and thyroid status was documented, based on hormonal measurements and clinical examinations. Results: There were 656 women (44.3%) that had at least one risk factor for thyroid diseases and were eligible for the targeted high-risk case finding (high-risk group) approach, while 55.7% had no risk factors (low-risk group). Using the universal screening approach, there were 974 women (65.8%) with normal thyroid status and 506 participants (34.2%) with thyroid disturbances, including overt hyperthyroidism (0.7%), overt hypothyroidism (1.1%), subclinical hypothyroidism (30.1%; positive TPOAb (5.5%) and negative TPOAb (24.6%); and euthyroid and positive TPOAb (2.3%). Of women with thyroid dysfunction, 64.4% were in the high-risk group and 35.6% were in the low-risk group (P<0.0001). Conclusions: The targeted high-risk case finding approach overlooks about one-third of pregnant women with thyroid dysfunction. If ongoing prospective trials provide evidence on the efficacy of treating subclinical hypothyroidism in pregnancy, in populations with a low prevalence of presumed risk factors, the targeted high-risk case finding approach will be proven inefficient. [ABSTRACT FROM AUTHOR]

Background: Management of thyroid diseases during pregnancy requires special considerations because maternal thyroid diseases can have adverse effects on both pregnancy and fetus. Universal screening for thyroid diseases in pregnant women is not currently supported by studies with high evidence whereas guidelines have been released for individuals at high risk, although controversies are still in debate. Iodine prophylaxis should be performed systematically to women during pregnancy.Materials and Methods: An electronic search of PubMed/Medline and EMBASE concerning thyroid diseases and pregnancy have been conducted over the past 20 years and summarized.Results: Data regarding prevention and treatment of thyroid diseases during pregnancy are reported from analysis of the literature.Conclusions: As thyroid dysfunction may cause profound impact on mother's and fetus's health, implementation by strict application of clinico-diagnostic flowchart and recommendations is of paramount importance when dealing with thyroid diseases during pregnant state. [ABSTRACT FROM AUTHOR]

Background Maternal clinical thyroid disorders can cause reproductive complications. However, the effects of mild thyroid dysfunctions are not yet well established. The aim was to evaluate the association of maternal thyroid function during the first half of pregnancy with birthweight and preterm delivery. Methods We analysed data on 2170 pregnant women and their children from a prospective population-based cohort study in four Spanish areas. Mid-gestation maternal serum and urine samples were gathered to determine thyroid-stimulating hormone ( TSH), free thyroxine ( fT4), and urinary iodine concentration ( UIC). Thyroid status was defined according to percentile distribution as: euthyroid ( TSH and fT4 >5th and <95th percentiles); hypothyroxinaemia ( fT4 < 5th percentile and TSH normal), hypothyroidism ( TSH > 95th percentile and fT4 normal or <5th percentile), hyperthyroxinaemia ( fT4 > 95th percentile and TSH normal), and hyperthyroidism ( TSH < 5th percentile and fT4 normal or >95th percentile). Response variables were birthweight, small and large for gestational age (SGA/LGA), and preterm delivery. Results An inverse association of f T4 and TSH with birthweight was found, the former remaining when restricted to euthyroid women. High fT4 levels were also associated with an increased risk of SGA [odds ratio, 95% confidence interval ( CI) 1.28 (95% CI 1.08, 1.51)]. Mean birthweight was higher in the hypothyroxinaemic group (β = 109, P < 0.01). Iodine intake and UIC were not associated with birth outcomes. Conclusions High maternal fT4 levels during the first half of pregnancy were related to lower birthweight and increased risk of SGA newborns, suggesting that maternal thyroid function may affect fetal growth, even within the normal range. [ABSTRACT FROM AUTHOR]

OBJECTIVE: To evaluate the efficacy of a targeted thyroid testing approach during pregnancy in clinical practice. METHODS: This is a retrospective cohort study per-formed within Uppsala County, Sweden. Data were derived from the population-based Uppsala Biobank of Pregnant Women, in which blood samples are collected in conjunction with the routine ultrasound screening in gestational week 17-19. For this study, 5,254 pregnant women with an estimated date of delivery between Jan-uary 1, 2009, and December 31, 2011, were included. On review of their medical records, women who were tested for thyroid dysfunction during pregnancy in clinical prac-tice were identified (n = 891). From the remaining untested women, 1,006 women were randomly selected for analyses of thyrotropin (TSH), free thyroxine levels, and thyroid peroxidase antibodies. Thyroid-stimulating hormone levels in both groups were analyzed with re-gard to trimester-specific upper reference levels as rec-ommended by the International Endocrine Society Guidelines. RESULTS: The proportion of trimester-specific TSH elevation was 12.6% in the targeted thyroid testing group and 12.1% in the untested group (P=.8; odds ratio [OR] 1.04, 95% confidence interval [CI] 0.79-1.37). The proportion of overt hypothyroidism was 1.1% and 0.7% in the groups, respectively (P=.4; OR 1.57, 95% CI 0.55-4.45). CONCLUSIONS: The prevalence of trimester-specific elevated TSH and overt hypothyroidism was equal in targeted thyroid tested and untested women. When implemented in clinical practice, targeted thyroid testing is unsatisfactory. If ongoing studies provide support for treatment of pregnant women with elevated TSH, uni-versal thyroid testing appears the most reasonable approach. [ABSTRACT FROM AUTHOR]

AIM: 1. To determine Thyroid dysfunction and antiTPO antibody status in pregnant women. 2. To know the benefit of LT4 therapy in maternal pregnancy outcome (antiTPO ab+ve vs antiTPO ab-ve groups) and 3. To determine the maternal and fetal outcomes in hypothyroid pregnant women and to decide whether universal screening of pregnant women for hypothyroidism is required or not. Materials and methods: A prospective study was done in mamata general hospital in the dept. of obg, over a period of 1 1/2 years. 105 antenatal women were included in the study. Outcome in these pregnancies were observed and analysed using appropriate statistical method .Results: There were only 3 patients with spontaneous abortions, 3 patients with pregnancy induced hypertension and only 1 patient had preterm delivery .There was more of thyroid dysfunction in anti TPO Ab +ve cases. But there was no significant adverse effect on pregnancy outcome in patients who were treated. Conclusion: Though our study included only a small number of antenatal women who were screened for thyroid abnormality since it was only a pilot study done in our hospital since our area is endemic for thyroid disorders due to iodine deficiency we recommend Universal screening to rule out thyroid dysfunction in pregnancy because the maternal and fetal complications can be reduced by early screening, diagnosing and correcting thyroid abnormality. [ABSTRACT FROM AUTHOR]

There is a well-known controversy among scientific societies regarding the recommendation to screen for thyroid dysfunction (TD) during pregnancy. Although several studies have shown an association between maternal subclinical hypothyroidism and/or hypothyroxinemia with obstetric problems and/or neurocognitive impairment in the offspring, there is only limited evidence on the possible positive effects of thyroxine (T4) treatment in such cases. Despite the scarcity of this evidence, there is a widespread agreement among clinicians on the need for treatment of clinical hypothyroidism during pregnancy and the risks that could arise due to therapeutic abstention. As maternal TD is a quite prevalent condition, easily diagnosed and for which an effective and safe treatment is available, some scientific societies have proposed to assess thyroid function during the first trimester of pregnancy and ideally before week 10 of gestational age. Given the physiologic changes of thyroid function during pregnancy, hormone assessment should be performed using trimester-specific reference values ideally based on locally generated data as geographic variations have been detected. Screening of TD should be based on an initial determination of TSH performed early during the first trimester and only if abnormal should it be followed by either a free or total T4measurement. Furthermore, adequate iodine supplementation during pregnancy is critical and if feasible it should be initiated before the woman attempts to conceive. [ABSTRACT FROM AUTHOR]

The primary objective of this study is to explore the influence of different screening strategies on the prevalence of thyroid dysfunction and the missed diagnosis during pregnancy. A total of 1889 pregnant women (13-27 weeks) were divided into high-risk and low-risk groups according to the backgrounds of them collected by questionnaire. We detected the prevalence of thyroid dysfunction in high-risk groups and low-risk pregnant women by normal reference range during the second trimester in our research. High-risk groups accounted for 10.69% of all the pregnant women in this study. Using targeted high-risk case screening strategy, misdiagnosis rate of pregnancy with hyperthyroidism, subclinical hyperthyroidism, pregnancy with hypothyroidism, subclinical hypothyroidism, low T4 syndrome and positive TPOAb were 87.5% (14 cases), 87.08% (155 cases), 87.08% (155 cases), 83.93% (47 cases), 89.47% (17 cases) and 88.35% (91 cases), respectively. Furthermore, there was no statistically significant difference between high-risk group and low-risk group in the prevalence of thyroid dysfunction. Therefore, we believe that universal screening to pregnant women can effectively reduce misdiagnosis rate of thyroid dysfunction. Further, we recommend universal screening for thyroid function in second trimester of pregnancy. [ABSTRACT FROM AUTHOR]

The article discusses the arguments on screening for thyroid dysfunctions that occur in pregnancy and analyzes the benefits and setbacks of newly proposed examinations of serum hormone levels, serum autoantibody levels, and use of clinical data. According to the article, the relevance of screening differs based on the content of iodine and selenium in food and water worldwide. Pertinent topics discussed include subclinical hypothyroidism, overt hypothyroidism, and thyroid autoantibodies.

Objective: The aim of this study was to investigate thyroid function tests in Gestational Diabetes Mellitus (GDM) and pre-gestational DM and control group. Methodology: There were 61 pregnant diabetic women in study group and 35 pregnant women in control group. Serum T4, T3, T3RU, FTI, TSH and Anti TPO Ab were assessed in each person. Results: About 36% of patients had GDM and 64% pre-gestational DM. Thyroid dysfunction was detected in 18% of study group compared with 8.6% of control group (P = 0.2). There was Thyroid dysfunction in 4.5% of GDM and 25.6% of pregestational DM (P = 0.045). There was no statistically significant difference between thyroid dysfunction in GDM group and control group (P=0.99).27% of GDM and 36% of pregestational DM and 23% of control group had positive titer of Anti TPO Ab without statistically significant differences among the three groups. Conclusion: Thyroid dysfunction is prevalent in women with pre-gestational DM so, thyroid function should be evaluated in these patients during pregnancy. Rate of thyroid dysfunction in GDM patients is similar to normal pregnant control women. High prevalence of positive titer of TPO Ab was seen in diabetic and nondiabetic pregnant women. [ABSTRACT FROM AUTHOR]

Introduction. Thyroid dysfunction during pregnancy may result in both maternal and neonatal complications. Subacute thyroiditis (SAT) is an extremely rare cause of both hyper- and hypothyroidism in pregnant women. Case description. A case of first trimester SAT is presented. Diagnosis of SAT was based on fine-needle aspiration biopsy. The disease resolved spontaneously without need for prednisone administration but a hypothyroid phase treated with T4 throughout pregnancy occurred. The pregnancy resulted in a healthy full term infant. We measured various cytokine levels in an attempt to follow their course during SAT as well as throughout the remaining period of pregnancy. Serum thyreoglobulin (Tg) levels correlated best with thyroid function tests (TFTs) and the course of SAT. Conclusions. The diagnosis of SAT at a pregnancy setting may be intriguing. The measurement of circulating cytokines is not helpful in the differential diagnosis or monitoring of the disease. [ABSTRACT FROM AUTHOR]

Postpartum thyroiditis is a potentially destructive lymphocytic thyroiditis occurring in approximately 8% of the pregnant population, making it the most common endocrine disorder associated with pregnancy. This autoimmune thyroid disorder is precipitated by the postpartum immunological rebound that follows the partial immunosuppression of pregnancy, in individuals already at risk of autoimmune thyroid disease. The manifestations of postpartum thyroiditis are usually not present at the six-week postpartum visit and thus it is important that all physicians be aware of the risks, presentation and intervention required for this common disorder. Postpartum thyroiditis is a strong predictor of future thyroid health and it is essential that women with a history of postpartum thyroiditis be screened regularly, especially prior to a future pregnancy. Selenium supplementation has recently been identified as a potential means to prevent postpartum thyroiditis in women at risk but further studies are required before recommendations for its use can be made. [ABSTRACT FROM AUTHOR]

OBJECTIVE: Screening of thyroid disorders in pregnancy has been controversial. Recent recommendations favour targeted high-risk case finding, though this approach may miss a significant number of those affected. We aimed to assess the prevalence of accepted high-risk criteria in women with autoimmune thyroiditis and/or hypothyroidism detected from universal screening in an iodine-sufficient population. DESIGN: In 400 non-selected women in the 9–11th gestational week, thyroid-related tests were performed, and those with abnormalities were offered consultation. METHODS: TSH was determined by IRMA, and the upper cut-off value for screening was set at 3.5 mIU/l. For free thyroxine (FT4) and thyroperoxidase antibodies (TPO-Ab), RIAs were used, with cut-offs of <10 pmol/l and >50 IU/ml respectively. Endocrinological consultation included Doppler ultrasonography and was aimed to confirm autoimmune thyroiditis and/or hypothyroidism. The prevalence of consensus high-risk criteria was assessed. RESULTS: Among the 400 women, 65 (16.3%) had ≥1 abnormality: higher TSH was found in 10.3%, lower FT4in 2% and positive TPO-Ab in 8.3%. Fifty-one women were examined and followed up. Levo-T4treatment was initiated in 49 women for autoimmune thyroiditis (in 42), hypothyroidism (in 34) or both (in 27). Only 22 (45%) of 49 treated women fulfilled ≥1 high-risk criterion: most commonly family history (31%), history of miscarriage or preterm delivery (14%) and personal history (8%). CONCLUSIONS: Over half (55%) of pregnant women with abnormalities suggestive of autoimmune thyroiditis and/or hypothyroidism would be missed if only those with high-risk criteria were examined. A more extensive screening of thyroid autoimmunity and dysfunction seems warranted. [ABSTRACT FROM AUTHOR]

Improvements in the sensitivity of the serum TSH assay have revolutionized our strategies for investigating thyroid function and firmly established TSH as the first-line thyroid function test for most clinical situations, including pregnancy. As a single hormone determination, serum TSH provides the most sensitive index to reliably detect thyroid function abnormalities. Normal thyroid function is important to ensure the best possible pregnancy outcome; in addition, disorders of the thyroid gland are relatively frequent in women of childbearing age. The aim of this article is, therefore, to present relevant information on analytical, as well as clinical, aspects regarding serum TSH determination and its usefulness to detect subtle thyroid function abnormalities associated with the pregnant state, namely overt and subclinical hypothyroidism and hyperthyroidism. As these disorders are associated with poor pregnancy outcome, the authors of the present article are in favor of serum TSH measurement for all pregnant women. [ABSTRACT FROM AUTHOR]

This JAMA Guidelines Synopsis summarizes the 2017 American Thyroid Association guidelines on diagnosis and management of thyroid disease during pregnancy and the postpartum period. [ABSTRACT FROM AUTHOR]

The article offers tips on managing thyroid disease in women planning to get pregnant. Ingestion of iron, calcium or prenatal vitamins should be separated from levothyroxine by at least four hours to prevent the supplements from interfering with thyroid hormone absorption. Women with active Graves disease or toxic adenoma are advised to delay pregnancy until normal thyroid function is established.

The author discusses the study conducted on the management of hypothyroid pregnant women in Tayside, Scotland using comprehensive databases. The author is particular over the wide variation of thyroid tests conducted in women despite the availability of local and international guidelines. The author expresses disappointments over the publications of high-profile international guidelines that showed suboptimal management of hypothyroidism among pregnant women.

Reports on the case of a 30-year-old pregnant woman with thrombocytopenia with absent radii (TAR), an autosomal recessive disorder. Diagnosis of hyperthyroidism at 10-weeks gestation; Instrumental delivery using Neville Barnes forceps after initial rotation using a ventouse cup; Characteristics of TAR.

OBJECTIVE: Transient elevation of serum free T4 (gestational transient hyperthyroxinaemia; GTH) occurs occasionally during normal pregnancy, especially in early gestation. However, the frequency of GTH and its clinical features remain unclear to date. The aim of this study was to determine the occurrence rate of GTH and the relation between serum levels of hCG, free T4 (fT4), and TSH in a large number of pregnant women. DESIGN: The four criteria of GTH were as follows: (1) no past history of thyroid disease, (2) negative tests for MCHA and TGHA, (3) no multiple pregnancies or trophoblastic disease and (4) transient hyperthyroxinaemia at less than 16 weeks of gestation. Thyroid function and hCG levels in 23 163 pregnant women were evaluated by mass sreening. If individual fT4 levels were more than the upper limit, blood re-sampling and the clinical and laboratory analysis of thyroid function were performed to exclude women with thyroid disease. The concentrations of hCG, fT4, and TSH in women with GTH and normal pregnant controls (n = 218) were compared. Regression analysis was performed for the comparison between hCG, fT4, and TSH levels in women with GTH. MEASUREMENTS: Blood samples were obtained using dried blood spots. Blood levels of fT4 was measured by radioimmunoassay, TSH and hCG were measured by fluoroimmunoassay. Anti-microsome antibody (MCHA) and anti-thyroglobulin antibody (TGHA) were measured by indirect agglutination reaction. RESULTS: GTH was observed in 66 of 23 163 women. The overall occurrence rate of GTH was 0.285%. In 22 of the 66 GTH women, serum TSH was undetectable. Using regression analyses, the concentration of fT4 was correlated with hCG levels in women with GTH (P < 0.05, r = 0.269), whereas the concentration of TSH was not correlated with hCG or fT4 level. The concentrations (M ± SD) of fT4, TSH, and hCG in women with GTH were 42.5 ± 12.3 pmol/l, 0.20 ± 0.31 mU/l and 190.2 ± 98.8 × 10[sup 3] IU/l, whereas... [ABSTRACT FROM AUTHOR]