Metabolites
First-Trimester Thyroid-Stimulating Hormone Levels and Gestational Diabetes Mellitus: A Retrospective Cohort Study
By Büşra Şahin, Tansu Bahar Gürbüz, Fazilet Tatar and 4 others.
Abstract
Background
The clinical relevance of a mildly elevated first-trimester thyroid-stimulating hormone (TSH) concentration is uncertain, recent meta-analyses disagree, and few studies have directly contrasted a TSH of 2.5–4.0 mIU/L with a TSH above 4.0 mIU/L.
Methods
In this single-centre retrospective cohort study, 218 singleton pregnancies with a first-trimester TSH ≥ 2.5 and ≤10.0 mIU/L and a concurrent free thyroxine (fT4) measurement were classified as high-normal TSH (2.5–4.0 mIU/L; n = 168) or elevated TSH (>4.0–10.0 mIU/L; n = 50; subclinical hypothyroidism in 47 and biochemically overt hypothyroidism in 3). The primary outcome was gestational diabetes mellitus (GDM); secondary outcomes were a composite obstetric complication, individual obstetric and neonatal outcomes, and first- and second-trimester screening markers. Two logistic regression models adjusted for maternal age were fitted; because levothyroxine was started after the index TSH measurement, it was treated as a potential intermediate and examined only in post hoc sensitivity analyses.