Search

Context: Thyroid hormones are critical for neural development, and during the first trimester of pregnancy the fetus relies fully on maternal thyroid hormone production., Objective: To investigate the associations between maternal thyroid hormone levels in the first trimester with the child's school performance, risk of attention deficit hyperactivity disorder (ADHD) and autism spectrum disorder (ASD)., Methods: From the Copenhagen Primary Care Laboratory Pregnancy Database information on first trimester TSH and fT4 measurements in mothers of children born in 2000-2014 were linked with information on the child's standardized test scores in school, ADHD (patient record diagnoses and medication) and ASD (patient record diagnoses) until end of 2018. Associations of TSH and fT4 with the outcomes were individually assessed by linear mixed models and Cox regression models. The analyses were stratified by preexisting maternal thyroid disorders., Results: TSH measurements were available for 17,909 mother-child dyads. Among those with children born in 2000-2009, 6,126 had a standardized school test score and were analyzed for the association between maternal thyroid hormone levels and child's school performance, and no support for an association was found. The association between thyroid hormone levels and child's risk of ADHD and ASD were analyzed for the 17,909 dyads and with no support for an association between thyroid hormone levels and these neurodevelopmental disorders. Stratification by preexisting maternal thyroid disorders did not affect the results., Conclusions: We found no evidence for associations between first trimester maternal thyroid hormone levels and child's school performance, or risk of ADHD or ASD., (© 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.)

Context: With age, the prevalence of subclinical hypothyroidism rises. However, incidence and determinants of spontaneous normalization remain largely unknown., Objective: To investigate incidence and determinants of spontaneous normalization of TSH levels in older adults with subclinical hypothyroidism., Design: Pooled data were used from the (1) pretrial population and (2) in-trial placebo group from 2 randomized, double-blind, placebo-controlled trials (Thyroid Hormone Replacement for Untreated Older Adults With Subclinical Hypothyroidism Trial and Institute for Evidence-Based Medicine in Old Age thyroid 80-plus thyroid trial)., Setting: Community-dwelling 65+ adults with subclinical hypothyroidism from the Netherlands, Switzerland, Ireland, and the United Kingdom., Participants: The pretrial population (N = 2335) consisted of older adults with biochemical subclinical hypothyroidism, defined as ≥1 elevated TSH measurement (≥4.60 mIU/L) and a free T4 within the laboratory-specific reference range. Individuals with persistent subclinical hypothyroidism, defined as ≥2 elevated TSH measurements ≥3 months apart, were randomized to levothyroxine/placebo, of which the in-trial placebo group (N = 361) was included., Main Outcome Measures: Incidence of spontaneous normalization of TSH levels and associations between participant characteristics and normalization., Results: In the pretrial phase, TSH levels normalized in 60.8% of participants in a median follow-up of 1 year. In the in-trial phase, levels normalized in 39.9% of participants after 1 year of follow-up. Younger age, female sex, lower initial TSH level, higher initial free T4 level, absence of thyroid peroxidase antibodies, and a follow-up measurement in summer were independent determinants for normalization., Conclusion: Because TSH levels spontaneously normalized in a large proportion of older adults with subclinical hypothyroidism (also after confirmation by repeat measurement), a third measurement may be recommended before considering treatment., Trial Registration: ClinicalTrials.gov, NCT01660126 and Netherlands Trial Register, NTR3851., (© The Author(s) 2023. Published by Oxford University Press on behalf of the Endocrine Society.)