Objective: In obese men, sex hormone-binding globulin (SHBG) as well as total testosterone (TT) levels are decreased. Data concerning serum free testosterone (FT) levels in obese men are discordant. FT levels are decreased in only some morbidly obese men, consistent with an impairment of the feedback regulatory mechanism. In this study we aimed to verify serum levels of TT and FT in two groups of obese men (BMI < 35.0 kg/m2 and BMI > 35.1 kg/m2) before and after weight loss.
Design: Two groups of obese men (group 1: BMI < or = 35 kg/m2; and group 2: BMI > or =35.1 kg/m2) were studied before and after 6 months of a low energy diet (1200 kcal/day). Every patient received a therapeutic prescription of dexfenfluramine (15 mg b.i.d.) that was maintained for 6 months.
Subjects: Thirty-seven obese men and 20 normal weight men.
Measurements: Serum sex hormones (TT and FT), serum luteinizing hormone (LH) and insulin were analyzed by RIA assays. Plasma insulin levels, serum TT, FT and LH concentrations were obtained before and after weight loss.
Results: Moderately obese men (BMI = 32.3+/- 1.9 kg/m2) presented significantly decreased TT levels (390+/-120ng/dl) as well as FT (mean+/-s.d.:16.0+/-4.8pg/ml) as compared with normal controls. FT serum levels had a significant and negative correlation with body mass index (BMI), whereas for TT concentrations this correlation was not significant. Serum LH concentrations (4.5+/-2.9mlU/ml) were normal. Insulin levels were elevated in all patients (46.3+/-30.1 microU/ml). After weight loss there was a significant (P< 0.01) increase in TT, FT and LH levels, whereas insulin concentrations significantly decreased. In massively obese men (BMI = 43.0 6.7 kg/m2), TT (320+/-110ng/dl), FT (11.0+/-2.1 pg/ml) and LH (3.1+/-1.3mlU/ml) were decreased and significantly lower as compared with the previous group and normal controls. As expected, after weight loss TT, FT and LH levels increased significantly while insulin concentrations decreased.
Conclusions: We concluded that FT levels are dependent on the degree of obesity, massively obese men (BMI > or =35.1 kg/m2) being considered as candidates for consistently low FT levels. A functional decrease of LH pulse amplitude and serum LH levels as well as a possible negative action of excess of circulating leptin on the steroidogenesis may be related to the decreased androgens levels in massively obese men.