Comparison of Thyroglobulin and Thyroid Function in Pregnant Women between Counties with a Median Urinary Iodine Concentration of 100-149 µg/L and 150-249 µg/L

Abstract

Objective: This study explored whether thyroglobulin and thyroid disease prevalence rates were higher in pregnant Chinese women with a median urinary iodine concentration of 100-149 µg/L, compared with those with a median urinary iodine concentration of 150-249 μg/L maintained through sustainable universal salt iodization.

Methods: This was a cross-sectional study in which 812 healthy pregnant women were enrolled to collect samples of their household edible salt, urine, and blood during their routine antenatal care in the 18 counties in Fujian Province, China. The levels of salt iodine concentration, urinary iodine concentration (UIC), free triiodothyronine (FT3), free thyroid hormone (FT4), thyroid-stimulating hormone (TSH), thyroglobulin (Tg), thyroid peroxidase antibody and thyroglobulin antibody were assessed during the routine antenatal care visits.

Results: The median UIC (mUIC) in pregnant women was 130.8 μg/L (interquartile range = 91.5-198.1 μg/L) in the counties with an mUIC of 100-149 μg/L (Group I), and 172.0 μg/L (interquartile range = 123.5-244.4 μg/L) in the counties with an mUIC of 150-249 μg/L (Group II). Goiter prevalence and thyroid nodule detection rates showed no difference between Group I and Group II ( P > 0.05). Except for FT4 values, the TSH, FT4, FT3, Tg and Tg values > 40 (μg/L) and the thyroid diseases prevalence rate (TDR) showed no significant differences between Group I and Group II ( P > 0.05), whether or not iodine supplementation measures were taken.

Conclusion: Compared with an mUIC of 150-249 μg/L, not only there was no difference in thyroid morphology, but also the Tg value, rate of Tg values > 40 µg/L, and TDR were not higher in pregnant women in the counties with an mUIC of 100-149 μg/L achieved through sustainable universal salt iodization in Fujian Province, China.

Keywords: Pregnant women; Thyroglobulin; Thyroid dysfunction; Urinary iodine concentration.