Serum iodine concentration and its associations with thyroid function and dietary iodine in pregnant women in the southeast coast of China: a cross-sectional study

Abstract

BackgroundIodine deficiency is a major public health problem in pregnant women. Serum iodine (SI) may represent a useful biomarker for iodine nutrition evaluation. We aimed to assess the relationship between serum iodine concentration (SIC) and urinary iodine concentration (UIC), dietary iodine, thyroid function, and thyroid diseases in pregnant women in the southeast coast of China, and to provide a normal reference range of SIC for pregnant women.MethodsA multistage random sampling method was used to select the study population. We collected urine and blood samples from pregnant women and determined UIC and SIC as well as thyroid function using Arsenic-Cerium Catalytic Spectrophotometry, inductively coupled plasma mass spectrometry, and Beckman Coulter Access2 chemiluminescent immunoanalyzer and kit, respectively, and administered a questionnaire on dietary iodine intake in pregnant women.ResultsThere was a significant negative correlation between SI and thyroid-stimulating hormone (TSH) (r = −0.141) and a significant positive correlation between SI and free triiodothyronine (FT3) (r = 0.106), free thyroxine (FT4) (r = 0.236), triiodothyronine (TT3) (r = 0.229), total thyroxine (TT4) (r = 0.433), and dietary iodine intake (r = 0.068). There was a significant difference in SI levels of pregnancy between the second (78.13 μg/L) and third trimester (75.37 μg/L) (p = 0.018). SI levels between inadequate intake (74.58 μg/L) and appropriate intake (77.92 μg/L) groups were statistically different (p = 0.036). Low SIC was a risk factor for the development of hypothyroxinemia (adjusted OR = 3.14, 95% confidence interval: 1.75–5.66). The reference range for SIC in normal pregnant women is 45.03–112.44 μg/L.ConclusionSI may be a composite indicator of iodine nutritional status and thyroid function.

Iodine nutritional status and its associations with thyroid function of pregnant women and neonatal TSH

“…Notably, these ranges were observed in regions with adequate iodine nutrition for the general population as well as areas where iodine supplementation was implemented. The suitable range of SIC in this study was basically consistent with the research findings of Ji et al (6) The suitable 24-hour UIE value exceeded that reported in Saudi Arabia (28). The suitable of Tg were lower than those documented in many studies (29).…”

“…Among these studies, one conducted in Shanghai (China) displayed that both low and high urine iodine concentration was related to thyroid function and autoimmunity (5). A cross-sectional study in the southeast coast of China showed that serum iodine concentration (SIC) negatively correlated with thyroid stimulating hormone (TSH), and positively correlated with other thyroid function indicators, which indicating SIC may serve as a composite indicator of iodine nutritional status (6). A study conduct in northern Spain indicated that the consumption of iodized salt was associated with adequate iodine nutrition but not with maternal thyroid function (7).…”