Diabetes mellitus is associated with subnormal serum levels of free testosterone in men.

OBJECTIVE To evaluate the relationship between diabetes mellitus (DM) and serum levels of free (FT) and total (TT) testosterone. PATIENTS AND METHODS A cross-sectional study was carried out including 746 men, of whom 116 (15.6%) were diabetics. Both groups, diabetic and nondiabetic, were paired according to age. Body mass index (BMI) and waist-to-hip ratio (WHR) were calculated, and a stratification analysis correlating DM and elevated BMI (>25 kg/m(2)) and WHR (>1) with the presence of subnormal FT and TT levels was performed. RESULTS FT and TT serum levels were subnormal in 46% and 34% of diabetics, respectively, and in 24% and 23% of nondiabetics. Subnormal FT levels were strongly correlated with DM (odds ratio (OR) 2.7; 95% confidence interval (CI) 1.8-4.1) but not with elevated BMI (OR 1.4; 95% CI 1.0-2.0). Subnormal TT levels were more strongly associated with elevated BMI and WHR (OR 2.6; 95% CI 1.7-3.9 and 2.0; 1.4-2.9) than with DM (1.7; 1.1-2.6 and 2.0; 1.3-3.2). CONCLUSION These data strongly suggest that DM is associated with subnormal FT levels, and that TT levels are influenced more by obesity and central adiposity.