The Iodine Status and Prevalence of Thyroid Disorders Among Women of Childbearing Age in China: National Cross-sectional Study

Objective Mandatory universal salt iodization in China was implemented 20 years ago. However, the current iodine status and prevalence of thyroid disorders among childbearing-age women are unknown. Methods A nationally representative cross-sectional study with 26 166 enrolled participants aged 18 to 49 years from all 31 provincial regions of mainland China was performed. The participants were given a questionnaire and underwent B-mode ultrasonography of the thyroid. The serum concentrations of thyroid hormones and thyroid antibodies and the urinary iodine concentration (UIC) were measured. Results The median UIC was 178.7 μg/L, indicative of adequate iodine status. pHowever, 19.04% and 19.87% of the participants were classified as having iodine deficiency and excessive iodine, respectively. The weighted prevalence of thyroid disorders was as follows: 1.08% had overt hyperthyroidism, 0.58% had subclinical hyperthyroidism, 0.76% had Graves disease, 1.28% had overt hypothyroidism, 14.28% had subclinical hypothyroidism, 13.53% were positive for thyroid peroxidase antibodies, and 14.55% were positive for thyroglobulin antibodies. Excessive iodine and overweight were associated with higher odds of subclinical hypothyroidism. A family history of thyroid disorders and an age between 40 and 49 years were significantly associated with higher odds of positivity for thyroid peroxidase antibodies and thyroglobulin antibodies. Conclusion Iodine deficiency, excessive iodine, subclinical hypothyroidism, and positivity for thyroid autoantibodies remain prevalent among women of childbearing age in China. Women of childbearing age who are relatively older, are overweight, or have a family history of thyroid disorders are encouraged to undergo active screening of their UIC and thyroid function when planning a pregnancy.