Progression of Gestational Subclinical Hypothyroidism and Hypothyroxinemia to Overt Hypothyroidism After Pregnancy: Pooled Analysis of Data from Two Randomized Controlled Trials

Authors

• Michael W Varner
• Lisa Mele
• Brian M Casey
• Alan M Peaceman
• Uma M Reddy
• Ronald J Wapner
• John M Thorp
• George R Saade
• Alan T N Tita
• Dwight J Rouse
• Baha M Sibai
• Maged M Costantine
• Brian M Mercer
• Steve N Caritis
• Eunice Kennedy Shriver National Institute of Child Health and Human Development Maternal-Fetal Medicine Units Network, Bethesda, MD, USA

Language

English

Publication Date

9-1-2024

DOI

10.1089/thy.2023.0616

PMID

39028022

PMCID

PMC11563732

PubMedCentral® Posted Date

9-17-2024

PubMedCentral® Full Text Version

Post-print

Abstract

Background: To examine the incidence of overt hypothyroidism 1 and 5 years after pregnancies where screening before 21 weeks identified subclinical hypothyroidism (SH) or hypothyroxinemia (HT). Methods: Secondary analysis of two multicenter treatment trials for either SH or HT diagnosed between 8 and 20 weeks gestation. Current analyses focus only on individuals randomized to the placebo groups in the two parallel studies. SH was diagnosed with thyrotropin (TSH) ≥4.0 mU/L and normal free T4 (fT4) (0.86-1.9 ng/dL). HT was diagnosed with normal TSH (0.08-3.99 mU/L) but fT4 < 0.86 ng/dL. Serum from initial testing was stored for later thyroid peroxidase (TPO) antibody assay; results were not returned for clinical management. At 1 and 5 years after delivery, participants were asked whether they had either been diagnosed with or were being treated for a thyroid condition. Maternal serum was collected at these visits and thyroid function measured. Subsequent overt hypothyroidism was defined as TSH ≥4.0 mU/L with fT4 < 0.86 ng/dL. Results: Data for 1- and 5-year follow-up were available in 307 of the 338 participants with SH and 229 of the 261 with HT. Subsequent hypothyroidism was more common both at year 1 (13.4% vs. 3.1%, p < 0.001) and year 5 (15.6% vs. 2.6%, p < 0.001) for participants with SH compared with those with HT. This progression was more common in individuals with TSH values >10 mIU/mL. Baseline TPO level >50 IU/mL in participants with SH was associated with higher rates of hypothyroidism at year 1 (26.7% vs. 6.5%, odds ratio [OR] = 5.3 [confidence interval (CI) 2.6-10.7]) and year 5 (30.5% vs. 7.5%, OR = 5.4 [CI: 2.8-10.6]) compared with those with TPO levels ≤50 IU/mL. For participants with HT, no differences in overt hypothyroidism were seen at 1 year related to baseline TPO level >50 IU/mL (1/10 (10%) vs. 6/218 (2.8%), OR = 3.9 [CI: 0.43-36.1]), but more participants with TPO levels >50 IU/mL developed hypothyroidism by year 5 (2/10 (20%) vs. 4/218 (1.8%), OR = 13.4 [CI: 2.1-84.1]). Conclusion: SH is associated with higher rates of overt hypothyroidism or thyroid replacement therapy within 5 years of delivery than is HT when these conditions are diagnosed in the first half of pregnancy.

Keywords

Adult, Female, Humans, Pregnancy, Disease Progression, Hypothyroidism, Incidence, Iodide Peroxidase, Pregnancy Complications, Thyroid Function Tests, Thyrotropin, Thyroxine

Published Open-Access

yes

Recommended Citation

Varner, Michael W; Mele, Lisa; Casey, Brian M; et al., "Progression of Gestational Subclinical Hypothyroidism and Hypothyroxinemia to Overt Hypothyroidism After Pregnancy: Pooled Analysis of Data from Two Randomized Controlled Trials" (2024). Faculty, Staff and Student Publications. 3915.
https://digitalcommons.library.tmc.edu/uthmed_docs/3915