Reference Intervals for Thyroid Hormones During the First Trimester of Gestation: A Report from an Area with a Sufficient Iodine Level

We examined 436 pregnant women in their first trimester of pregnancy, and 444 non-pregnant women in a cross sectional study. Serum levels of thyroid stimulating hormone (TSH), free thyroxin (FT4), free triiodothyronine (FT3), thyroid peroxidase antibody, urinary iodine concentration (UIC), and thyroid volume were measured for all subjects. The first trimester-specific reference intervals (2.5th–97.5th percentile) were determined for 185 pregnant women and 256 non-pregnant women with negative TPOAb, adequate iodine level (UIC≥150 μg/l in pregnant and UIC≥100 μg/l in non-pregnant women), and normal thyroid examination. We calculated multiples of the median (MoM) for TFTs to normalize the obtained data. The first trimester-specific reference intervals of serum TSH, FT4, and FT3 for pregnant women were 0.20–4.60 mIU/l, 9.0–18.02 pmol/l, and 3.40–5.64 pmol/l, respectively, while the corresponding figures for non-pregnant women were 0.59–5.60 mIU/l, 9.52–19.30 pmol/l, and 3.70–5.55 pmol/l, respectively. The first and 99th percentile MoM of TSH in pregnant women in their first-trimester was 0.06–4.62. The local normal reference ranges for the first trimester of pregnancy in central region of Iran were different from the ranges suggested by the ATA. [...] © Georg Thieme Verlag KG Stuttgart · New YorkArticle in Thieme eJournals: Table of contents  |  Abstract  |  Full text
Source: Hormone and Metabolic Research - Category: Endocrinology Authors: Tags: Endocrine Care Source Type: research