Relationship of prostate-specific antigen to age and testosterone in men with type 2 diabetes mellitus

Objective: To determine whether prostate-specific antigen (PSA) concentrations in type 2 diabetic men with hypogonadotrophic hypogonadism are lower than those in eugonadal men with type 2 diabetes and whether PSA concentrations are related to plasma testosterone concentrations. Methods: In this cross-sectional study, we measured serum total testosterone, sex hormone-binding globulin, free testosterone, PSA, hematocrit, and hemoglobin A_1c in consecutive type 2 diabetic men who presented to 2 endocrinology referral centers between January 2006 and January 2007. We collected other clinical and demographic data including age, height, weight, and ethnicity. Results: Of 400 eligible patients, 280 men met inclusion criteria. Plasma PSA concentrations were lower in type 2 diabetic men with low free testosterone concentrations than in those with normal free testosterone concentrations (25.65 ± 2.02 ng/dL vs 31.70 ± 2.31 ng/dL, P = .011). PSA concentrations were positively related to age (r = 0.34, P<.001), total testosterone (r = 0.29, P<.001), free testosterone (r = 0.17, P = .02), and sex hormone-binding globulin (r = 0.22, P<.001) and negatively related to body mass index (r = -0.28, P<.001). In stepwise backward regression analysis, PSA concentration was predicted by age (P<.001) and free testosterone (P<.001), but not by body mass index or sex hormone-binding globulin. Conclusions: Plasma PSA concentrations are lower in type 2 diabetic men with hypogonadism than in eugonadal men with type 2 diabetes, and plasma PSA is related to age, plasma total testosterone concentrations, and free testosterone concentrations in patients with type 2 diabetes.