Abstract
Objective: The aim of this study was to assess thyroid volume and thyroid function during pregnancy in an iodine-replete area in women with normal and subnormal Urinary Iodine Concentration (UIC).
Methods: In 465 pregnant Tehranian women ultrasound thyroid volume, UIC and serum T4 and TSH measurements were performed during the first, second and third trimesters of pregnancy. Based on median UIC (MUIC) in 3 consecutive days during the first trimester, women were divided into groups I and II with MUIC of <150 and ≥150 µg/L, respectively.
Results: Mean age was 25.6±5.1 years. MUIC in group I and II were: 123 and 250, 127 and 166, 120 and 150 µg/L in the first, second and third trimester, respectively. MUIC declined significantly only in group II (p<0.001). The median thyroid volume increased from 7.8 to 8.2 and 8.1 in group I and from 7.5 to 8.0 and 8.4 ml in group II, (p<0.002 in both groups). Serum TSH was 2.3±2.6, 2.1±1.8, 2.3±1.7 in group I and 2.1±3.1, 2.1±1.8 and 2.0±1.3 mU/L in group II during the first, second and third trimesters (NS). The mean serum T4 did not differ between groups in each trimester. There was no correlation between thyroid volume and UIC, T4 or TSH throughout trimesters.
Conclusion: In iodine replete pregnant women, there is no difference in thyroid volume and function between those having UIC <150 and ≥150 µg/L.