Circulating free testosterone in obese men after bariatric surgery increases in parallel with insulin sensitivity
Botella-Carretero JI, Balsa JA, Gómez-Martin JM, Peromingo R, Huerta L, Carrasco M, Arrieta F, Zamarron I, Martin-Hidalgo A, Vazquez C. J Endocrinol Invest. 2012 Jun 25. [Epub ahead of print]


Unit of Clinical Nutrition and Obesity, Department of Endocrinology and Nutrition, Madrid, Spain.


Background and Aim: Male hypogonadism has been linked to obesity and diabetes. We aimed to study the association of changes in insulin sensitivity and testosterone levels in severe obese patients submitted to bariatric surgery. Subjects and Methods: Prospective intervention study with twenty consecutive patients who underwent bariatric surgery studied before and after significant weight loss. Serum testosterone, sex hormone binding globulin, fasting glucose and insulin were measured among others. Free testosterone was calculated with the Vermeulen formulae and insulin sensitivity by the homeostatic model assessment. Results: At baseline, thirteen patients had low total testosterone levels, whereas eight of these patients also had free testosterone levels below the reference range obtained from the control group. After bariatric surgery total testosterone, SHBG and free testosterone significantly increased and achieved normal values in all evaluated patients. Insulin sensitivity improved in all of them. Multivariate linear regression showed that changes in fasting glucose (β = -1.868, P = 0.001), insulin (β = -3.782, P = 0.001), weight (β = -0.622, P = 0.002), and SHBG (β = - 0.635, P = 0.022) were associated with changes in free testosterone (adjusted R2 = 0.936, F = 26.613, P = 0.001). When insulin resistance calculated by HOMA was in the model instead of insulin and glucose, it also was associated (β = -3.488, P = 0.008) with free testosterone (adjusted R2 = 0.821, F = 11.111, P = 0.005). Conclusion: Circulating testosterone in obese men increases after bariatric surgery in parallel with an improvement in insulin sensitivity.