Abstract
BackgroundPregnant 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.MethodsA 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.ResultsThe 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.ConclusionInadequate 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.
Highlights
Thyroid autoimmunity is one of the most prevalent organ-specific autoimmune diseases
Participants who consumed non-iodized salt had a significantly higher proportion of urinary iodine concentration (UIC) < 100 μg/L (36.9% vs. 33.1%; p = 0.04); this was true for participants in middle (37.9% vs. 31.1%; p = 0.018; Fig. 2) and late (45.3% vs. 37.1%; p = 0.015; Fig. 2) pregnancy as well
General characteristics and thyroid disease spectrum stratified by the type of salt used Table 1 shows general characteristics and the thyroid disease spectrum stratified by the type of salt used
Summary
Thyroid autoimmunity is one of the most prevalent organ-specific autoimmune diseases It is usually characterized by the presence of antibodies against thyroidspecific components such as thyroglobulin, thyroid peroxidase, and thyrotrophic receptor antigen. Thyroid autoimmunity was much more common among women than in men, with the female: male ratio ranging from 5:1 to 10:1. This sex difference may be related to changes in antibodies during pregnancy [3,4,5]. 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
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