The aim of this study was to assess the correlation between the distribution of adipose tissue, sexual hormones and hyperinsulinemia in male obesity. Fifty-two obese males, aged 40.0 +/- 10.9 years old and with a body mass index (BMI) of 35.0 +/- 6.1 (m +/- SD), not suffering from diabetes or any other endocrine disease, were included in the study. A group of 20 subjects aged 30.5 +/- 7.9 (p less than 0.005 vs obese subjects) and with a BMI of 23.0 +/- 2.0 were used as controls. Body fat distribution was assessed using the waist/hip ratio (w/h ratio): 0.985 +/- 0.052 in obese subjects and 0.913 +/- 0.061 in controls (p less than 0.005). In comparison to control subjects, significantly lower levels of total (T) (357 +/- 132 vs 498 +/- 142 ng/dl; p less than 0.005) and free testosterone (FT) (14.2 +/- 2.9 vs 17.1 +/- 2.6 pg/ml; p less than 0.05) were found in the obese group, as well sex hormone binding globulin (SHBG) (41.7 +/- 31.9 vs 66.2 +/- 18.6 nmol/l; p less than 0.001). None of the other steroids (androstenedione, dehydroepiandrosterone-sulphate, estrone, 17 beta-estradiol, dihydrotestosterone) or FSH and LH gonadotropins assayed differed between the two groups. Significantly higher levels of insulin and C-peptide, both fasting and after a oral glucose tolerance test, were also found in obese subjects.(ABSTRACT TRUNCATED AT 250 WORDS)