Effect of Roux-en-Y gastric bypass on thyroid function in euthyroid patients with obesity and type 2 diabetes

Abstract

BackgroundThe impact of bariatric surgery on thyroid hormone levels is poorly understood. ObjectivesTo investigate changes in serum-free thyroxine (FT4) and thyroid-stimulating hormone (TSH) after Roux-en-Y gastric bypass (RYGB) in euthyroid patients with obesity and type 2 diabetes. SettingUniversity Hospital, China. MethodsEighty-one euthyroid Chinese patients with obesity and type 2 diabetes who underwent RYGB, and 20 healthy volunteers were enrolled in this retrospective study. Participants were evaluated for changes in anthropometric parameters, metabolic indexes, FT4, and TSH at baseline and 6 months after surgery. Multiple linear regression analysis was used to identify factors that could predict changes in FT4 and TSH. ResultsMean FT4 levels decreased from 16.26–14.59 pmol/L (P<.01), while TSH levels decreased significantly (2.19±1.09 mIU/L versus 1.97±1.12 mIU/L, P = .027) 6 months postsurgery. Multiple linear regression analysis showed that the waist/hip ratio (β =−7.406, P = .031) and duration of diabetes (β =−.087, P = .009) were independent factors contributing to this decrease in FT4 levels. Moreover, changes in TSH levels were significantly and positively correlated with 2-hour postprandial blood glucose at patient baseline (β = .064, P< .01). ConclusionsThe present study is the first to show that both serum levels of FT4 and TSH decrease after RYGB in euthyroid patients with obesity and type 2 diabetes. Our results suggest that not only can RYGB improve metabolic abnormalities, but it may also alter the feedback regulation of the thyroid system.