Associations of noniodized salt and thyroid nodule among the Chinese population: a large cross-sectional study

Background: The controversy that iodized salt may increase the risk of thyroid disorders has arisen in China during the past several years. Objective: This study aimed to explore whether iodized salt increased the risk of thyroid nodule among a Chinese population. Design: A cross-sectional study was conducted in Hangzhou, China, in 2010. Iodized salt intake, urinary iodine concentration (UIC), and thyroid nodule (by ultrasonography) were measured in 9412 adults. The associations of iodized salt with thyroid nodule were evaluated by using multiple mixed logistic regression models. Results: The prevalence of thyroid nodule among men and women was 24.1% and 34.7%, respectively. Adults consuming noniodized salt had an increased risk of thyroid nodule (OR: 1.36; 95% CI: 1.01, 1.83). Similarly, compared with moderate salt appetite, mild salt appetite was associated with an increased risk of thyroid nodule among all adults (OR: 1.19; 95% CI: 1.03, 1.37) and among women (OR: 1.23; 95% CI: 1.03, 1.46). Furthermore, those who consumed neither iodized salt nor milk had a higher risk of thyroid nodule (OR: 1.72; 95% CI: 1.21, 2.43) than did those who consumed both iodized salt and milk. In addition, an increased risk of thyroid nodule (OR: 1.25; 95% CI: 1.07, 1.45) was observed among both pooled samples and women with low UIC. Conclusions: These findings indicate that low iodine intake may increase the risk of thyroid nodule in a Chinese population, particularly in women. Hence, the Universal Salt Iodization program may be indispensable for a coastal Chinese population such as that living in Hangzhou. This trial was registered at clinicaltrials.gov as NCT01838629.