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

Background: The impact of bariatric surgery on thyroid hormone levels is poorly understood. Objectives: To investigate changes in serum-free thyroxine (F14) and thyroid-stimulating hormone (TSH) after Roux-en-Y gastric bypass (RYGB) in euthyroid patients with obesity and type 2 diabetes. Setting: University Hospital, China. Methods: Eighty-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. Results: Mean 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 (beta = -7.406, P =.031) and duration of diabetes (beta=-.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 (beta=-.064, P <.01). Conclusions: The 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. (C) 2017 American Society for Metabolic and Bariatric Surgery. All rights reserved.