Iodine nutrition status and thyroid autoimmunity during pregnancy: a cross-sectional study of 4635 pregnant women

Abstract

Background Pregnant women in Shanghai have long been at risk for mild iodine deficiency. Because thyroid autoimmunity in pregnant women can lead to premature birth and miscarriage as well as neurodevelopmental deficits in the fetus, the aim of this study was to explore the association of iodine nutrition status with thyroid antibodies during pregnancy. Methods A pregnancy-birth cohort was conducted including 4635 pregnant women in Shanghai, China. The eligible participants underwent a face-to-face interview and completed questionnaire surveys to collect baseline information and diet intake. Spot urine samples were collected to test urine iodine. Thyroid antibodies including thyroid peroxidase antibodies (TPOAb), thyroglobulin antibodies (TgAb) and thyrotrophic antibodies (TRAb) were tested. Single-factor analysis and logistic regression were used to evaluate the association between iodine status and thyroid autoimmunity during pregnancy. Results The median urinary iodine excretion level in the sample was 138.14 μg/L (interquartile range [IQR] 80.90–219.00 μg/L). Among all the subjects, 25.9% consumed non-iodized salt, 54.5% had iodine deficiency, and 31.0% had thyroid autoimmunity. The proportion of patients with iodine deficiency was significantly higher among those who consumed non-iodized salt (36.9% vs. 33.1%; p = 0.04). After adjusting for age, educational status, former smoker status, former drinker status, first pregnancy, and previous thyroid disease, non-iodized salt (odds ratio [OR] = 1.394 [confidence interval, CI, 1.165–1.562]; p = 0.003), iodine-rich food (OR = 0.681 [CI 0.585–0.793]; p = 0.003), iodized nutritional supplements (OR = 0.427 [CI 0.347–0.526]; p = 0.003), were found to be individually associated with thyroid autoimmunity in all participants. The results of the multivariable restricted cubic spline regression analysis showed a non-linear relationship between the continuous change in iodine intake and thyroid autoimmunity (p = 0.019). Participants with iodine deficiency (urinary iodine concentration, UIC,< 100 μg/L) had an increased risk of testing positive for thyroid antibodies (TPOAb/TgAb/TRAb[+]; OR = 1.324 [CI 1.125–1.559]; p < 0.001). Moreover, this associated existed even after removing participants with previous thyroid disease. Conclusion Inadequate iodine nutrition in pregnant women is an independent risk factor for thyroid autoimmunity in Shanghai. It’s important to maintain the adequate iodine status in pregnant women.

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

“…In this study, the median UI of pregnant women was 148.40 mg/ L < 150 mg/L, indicating mild iodine deficiency in pregnant women in Fujian Province, which was similar to our previous study and the results in coastal China (3,17,35,36). Similar to provinces like Fujian, pregnant women in some developed countries also face iodine deficiency, such as those in Austria, Norway, and Sweden (37,38).…”

“…Nearly 2 billion people worldwide still suffer from inadequate iodine intake (2). China used to have a high prevalence of iodine deficiency disorders (IDDs) (3).…”

Study on the relationship between serum iodine and dysfunctions: a cross-sectional study

“…In male subjects, the positive rates of TgAb and TPOAb were not affected by serum iodine levels, while in female subjects, lower serum iodine levels increased the positive rates of TgAb and TPOAb. A study on pregnant women also found that low serum iodine would increase the positive rate of TgAb, TPOAb [30]. The speci c reason is still unclear, and further research is still needed to clarify the mechanism.…”

The Interactive Effects of Severe Vitamin D Deficiency and Iodine Nutrition Status on the Risk of Thyroid Disorder in Pregnant Women

“…Urine collection and the iodine urinary test method were carried out according to the methods detailed in our published articles [ 18 ]. Iodine status was categorized as follows: insufficiency (urinary iodine concentration (UIC) less than 150 μg/L) (low UIC); adequate (UIC more than 150 μg/L and less than 249 μg/L); above requirements (UIC more than 250 μg/L) (high UIC) [ 19 ].…”