Association of thyroid nodules with adiposity: a community-based cross-sectional study in China

Background: The association between thyroid nodules and adiposity remains controversial. We performed a cross-sectional, community-based study to examine whether thyroid nodules are associated with overweight and obesity, as defined with body mass index (BMI) and waist circumference. Methods: The study included 1482 subjects (>= 20 years of age; residing in Nanjing, China) receiving questionnaire interview, anthropometric measurements, laboratory tests and thyroid ultrasonography in 2009-2010. Overweight and obesity were defined as BMI >= 24 and >= 28 kg/m(2), respectively. Central obesity was defined as waist circumference at >= 90 cm in men and >= 80 cm in women. A sensitivity analysis was conducted using the American Diabetes Association (ADA) criteria for overweight and obesity (BMI >= 23 and >= 25 kg/m(2)). Results: Thyroid nodules were identified in 12.6% of the subjects. A greater proportion of the subjects with thyroid nodules had a BMI at >= 24 kg/m2 (51.9% vs. 40.5% in those without thyroid nodules, P = 0.003) and central obesity (43. 3% vs. 24.2%, P < 0.001). After adjustment for other confounders, central obesity was still associated with significantly elevated risk of thyroid nodules (OR 1.62, 95% CI 1.14-2.28), whereas obesity/overweight based on BMI was not in both the main analysis and sensitivity analysis with the alternative criteria. In the subgroup analysis, BMI >= 24 kg/m(2) (OR 1.61, 95% CI 1.01-2.54), as well as BMI >= 25 kg/m(2) (OR 1.95, 95% CI 1.14-3.34), was significantly associated with higher risk of thyroid nodules among women. Using the ADA criteria, overweight and obesity were associated with thyroid nodules (OR 5.59, 95% CI 1.39-22.51 and 5.15, 95% CI 1.30-20.37) in thyroid-stimulating hormone (TSH) > 4.2 mIU/L subgroup. Central obesity correlated with higher risk of thyroid nodules regardless of age (< 50 years: OR 1.87, 95% CI 1.05-3.32: >= 50 years: OR 1.54, 95% CI 1.00-2.37) and in the following subgroups: men (OR 1.91, 95% CI 1.14-3.20), TSH > 4.2 mIU/L (OR 3.05, 95% CI 1.01-9.22), and urine iodine >= 200 mu g/L (OR 1.79, 95% CI 1.14-2.81). Conclusion: Waist circumference is superior to BMI for assessing risk of thyroid nodules in Chinese subjects.