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Medical Science Monitor Basic Research


eISSN: 1643-3750

Association Between Body Mass Index and Thyroid Function in Euthyroid Chinese Adults

Jing Fu, Lin Zhang, Yu An, Yan Duan, Jia Liu, Guang Wang

Department of Endocrinology, Beijing Chaoyang Hospital, Capital Medical University, Beijing, China (mainland)

Med Sci Monit 2021; 27:e930865

DOI: 10.12659/MSM.930865

Available online: 2021-03-09

Published: 2021-03-19


BACKGROUND: Obesity can influence thyroid function through multiple routes, even in people who are euthyroid. The correlation between weight and thyroid function is a matter of debate. The present study investigated the relationship between body weight and thyroid function in euthyroid Chinese adults.
MATERIAL AND METHODS: A total of 1564 participants with serum thyrotropin (TSH) and thyroid hormone levels within the reference range were included. All of them were tested for thyroid function parameters and categorized, based on body mass index (BMI), into 3 groups: normal weight, overweight, and obese. The effects of BMI on thyroid function were examined using linear (continuous values) and logistic (dichotomous levels according to medians or means) regression and controlling for age and sex.
RESULTS: There were significant differences in free triiodothyronine (FT3) levels and FT3/free thyroxine (FT4) ratios among participants who were normal weight, overweight, and obese (both P<0.001). Multivariable regression analysis (P<0.001) showed that BMI was positively associated with FT3 levels and FT3/FT4 ratios. Compared with the normal weight group, the patients who were overweight or obese had significantly higher FT3 levels and FT3/FT4 ratios that were higher than average, according to logistic regression analyses.
CONCLUSIONS: We found that Chinese adults who are obese may have higher FT3 levels and FT3/FT4 ratios than those who are of normal weight, even if their thyroid function values are within the normal range.

Keywords: Body Mass Index, Obesity, Thyroid Function Tests