The effects of metformin and diet on plasma testosterone and leptin levelsin obese men

Objective: The aim of this study was to investigate the effects of combined hypocaloric diet and metformin on circulating testosterone and leptin leve ls in obese men with or without type 2 diabetes. Research Methods and Procedures: Twenty obese men with type 2 diabetes (mea n body mass index [BMI]: 35.5 +/- 1.1 kg/m(2)) and 20 nondiabetic obese men were enrolled in the study. We measured serum follicle-stimulating hormone , luteinizing hormone (LH), total testosterone (TT), free testosterone (FT) , sex-hormone-binding globulin (SHBG), dehydroepiandrosterone sulfate (DHEA S), and plasma leptin levels before and 3 months after metformin treatment. Both groups were placed on a hypocaloric diet and 850 mg of metformin take n orally twice daily for 3 months. Results: Metformin and hypocaloric diets led to decreases in BMI and waist and hip circumferences in both groups. A significant decrease in TT levels in the diabetic group and FT levels in the control group was found, whereas follicle-stimulating hormone, LH, and DHEAS levels were not changed signif icantly. A significant increase in SHBG levels was observed in the control group but not in the patient group. Leptin levels also decreased after trea tment in both groups. Decreased testosterone levels were not correlated to changes in waist and hip circumference, waist-to-hip ratio, BMI, and levels of fasting blood glucose, leptin, SHBG, or DHEAS in the diabetic group. Ho wever, a decrease in FT was correlated to changes in the levels of SHBG (r = -0.71, p = 0.001) and LH (r = 0.80, p = 0.001) but not to other parameter s. Discussion: We conclude that metformin treatment combined with a hypocalori c diet leads to reduced FT levels in obese nondiabetic men and to reduced T T levels in obese men with type 2 diabetes. Increased SHBG levels may accou nt for the decrease in FT levels in the former group.