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Description
The obesity epidemic has reached alarming numbers, with about two thirds of U.S. adults being overweight or obese. The problem is multi-faceted and requires the understanding of different areas in order to effectively address the growing obesogenic population and begin to reverse the current trends. The present study is cross-sectional in design and aimed at understanding the association between thyroid function and obesity in individuals with normal thyroid function. A second aim of the study was to look at the association between iodine intake and BMI. The study evaluated data for 1692 euthyroid participants between the ages of 20 years and 49 years old. The study was conducted using data from the National Health and Nutrition Examination Survey for 2007-2008. Polychotomous logistic regressions were employed for multivariate analysis. All analyses were weighted and survey procedures were used to ensure accurate analysis given the complex study design of the data. The outcome of interest was BMI, which was categorized into the traditional cutpoints of normal, overweight and obese. The two main risk factors were serum thyroid-stimulating hormone levels (TSH) and urinary iodine concentration. Findings showed a positive association between TSH levels and BMI. The relationship between TSH and BMI was different among racial groups and among different smoking status categories. Final analysis was stratified by racial and smoking status categories. Findings revealed a significant positive association between TSH levels and BMI among non-Hispanic Whites, Hispanic/Latinos, non-Hispanic Blacks and non-smokers. These associations were significant for those being obese compared to those being normoweight. Noteworthy was the finding among Hispanic/Latinos being overweight relative to being normoweight. The association for these participants was negative, suggesting a decrease in odds of being overweight compared to normoweight for every 1-unit increase in TSH levels. Iodine was also found to be associated with BMI after adjusting for TSH and other factors. A significant negative association was found among Hispanic/Latinos, non-Hispanic Blacks and non-smokers only. Among Hispanic/Latinos and non-smokers, a significant association was found only when comparing obese and normoweight and only for iodine insufficiency relative to iodine sufficiency. Among non-Hispanic Blacks, an association was found when comparing overweight and normoweight for iodine insufficiency and excess compared to iodine sufficiency; and when comparing obese and normoweight for iodine insufficiency and excess relative to iodine sufficiency.
