Sex-Dependent Association between Weight Change and Thyroid Dysfunction: Population-Level Analysis Using the Korean National Health and Nutrition Examination Survey

Background Although body weight change (BWC) is a common manifestation of thyroid dysfunction, solid evidence for whether to perform or on whom to perform thyroid function test in subjects complaining of BWC is lacking. Objective To evaluate the association between thyroid dysfunction and BWC using a nationwide survey. Method Data was obtained from the Korea National Health and Nutrition Examination Survey VI 2013-2015 and 5,456 subjects without previous thyroid disease were included. Serum thyroid-stimulating hormone (TSH), free T4, and self-reported BWC during the previous year were used for the evaluation. Weight loss or gain was defined as weight change of at least 3 kg. Results In total, 1,017 men (37.3%) and 1,175 women (43.0%) reported BWCs during the previous year. The overall weighted prevalence of thyroid dysfunction was not significantly associated with the extent of BWC in men (p = 0.705) or women (p = 0.094). However, when the impact of TSH levels on weight change was separately evaluated for weight gain and loss after adjusting for age and body mass index in each sex, weight loss in women was significantly associated with TSH levels (hazard ratio 0.64, 95% CI 0.47-0.85, p = 0.03). No association of thyroid dysfunction was observed for weight gain in women (p = 0.23) or any changes in men (p = 0.875 in weight gain, p = 0.923 in weight loss). Conclusions This study highlights the necessity of performing thyroid function testing in women who complain of weight loss, but such testing may be less vital in women with weight gain or men with any changes in weight.