Association between iodine intake and thyroid autoantibodies: a cross-sectional study of 7073 early pregnant women in an iodine-adequate region
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The association between iodine intake and thyroid autoimmunity has been debated, especially in pregnant women. This study aimed to investigate thyroid autoantibodies and their association with iodine intake and hypothyroidism in early pregnancy.
7073 early pregnant women from an iodine-sufficient region participated in this study. Urinary iodine concentrations (UICs) were measured using an ammonium persulfate method. Serum thyroid peroxidase antibody (TPOAb), thyroglobulin antibody (TgAb), thyroid-stimulating hormone (TSH), free thyroxine (FT4), and Tg were determined using an electrochemiluminescence immunoassay.
Iodine deficiency (UIC < 100 μg/L) was associated with higher risks of TPOAb positivity [adjusted odds ratio (aOR) = 1.64, 95% confidence interval [CI] (1.29–2.08)] and TgAb positivity [aOR = 1.44, 95% CI (1.16–1.80)]. Women with isolated TPOAb positivity, isolated TgAb positivity, or both TPOAb and TgAb positivity had a 14.64-fold, 7.83-fold, and 44.69-fold increased risk of overt hypothyroidism, and a 4.36-fold, 2.86-fold, and 6.26-fold increased risk of subclinical hypothyroidism, respectively. Moreover, the risks of overt and subclinical hypothyroidism in women with a high TPOAb titer were 16.99 and 4.80 times that in TPOAb-negative women, respectively. The risk of overt hypothyroidism in women with a high TgAb titer was 6.97 times that in TgAb-negative women.
Our work demonstrates that iodine deficiency during early pregnancy is an independent risk factor for both TPOAb positivity and TgAb positivity. Furthermore, positivity for both autoantibodies and a high thyroid autoantibody titer are associated with significantly higher risks of overt and subclinical hypothyroidism.
KeywordsEarly pregnancy Iodine intake Thyroid autoantibodies Hypothyroidism
This work was supported by the 973 Science and Technology Research Foundation, Ministry of Science and Technology in China (Grant No. 2011CB512112); the Chinese National Natural Science Foundation (Grant No. 81 170 730); the Health and Medicine Research Foundation, Ministry of Health in China (Grant No. 201 002 002); the Research Foundation, Department of Science and Technology, Liaoning Province government, China (Grants No. 2012225020 and 2011225023); the Guanghua Science and Technology Foundation of China (Grant No. 2007-02); the Research Foundation of Key Laboratory of Endocrine Diseases, Department of Science and Technology, Shenyang Government, Liaoning Province, China (Grant No. F11-244-1-00); the Research Foundation innovative team from the Advanced Educational Institute (Grant No. LT 2 012 015); and the Twelve-Five Science and Technology Support Program (Grant No. No2014BAI06B02), as well as the important platform of science and technology for the universities in Liaoning Province (16010). We gratefully acknowledge the contributions of physicians from the gynecology and obstetrics clinics of 13 hospitals and 6 prenatal clinics in Liaoning Province. We thank the residents who participated in this study.
Compliance with ethical standards
Conflict of interest
The authors have no potential conflict of interest to declare.
All procedures performed in studies involving human participants were in accordance with the ethical standards of China Medical University and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards. The study was approved by the Medical Ethics Committee of China Medical University.
Informed consent was obtained from all individual participants included in the study.
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