Long-Term Effects of Dihydrotestosterone Treatment on Prostate Growth in Healthy, Middle-Aged Men Without Prostate Disease A Randomized, Placebo-Controlled Trial

Background: Benign prostatic hypertrophy increases with age and can result in substantially decreased quality of life for older men. Surgery is often required to control symptoms. It has been hypothesized that long-term administration of a nonamplifiable pure androgen might decrease prostate growth, thereby decreasing or delaying the need for surgical intervention. Objective: To test the hypothesis that dihydrotestosterone (DHT), a nonamplifiable and nonaromatizable pure androgen, reduces late-life prostate growth in middle-aged men. Design: Randomized, placebo-controlled, parallel-group trial. (Australian New Zealand Clinical Trials Registry number: ACTRN12605000358640) Setting: Ambulatory care research center. Participants: Healthy men (n = 114) older than 50 years without known prostate disease. Intervention: Transdermal DHT (70 mg) or placebo gel daily for 2 years. Measurements: Prostate volume was measured by ultrasonography; bone mineral density (BMD) and body composition were measured by dual-energy x-ray absorptiometry; and blood samples and questionnaires were collected every 6 months, with data analyzed by mixed-model analysis for repeated measures. Results: Over 24 months, there was an increase in total (29% [95% CI, 23% to 34%]) and central (75% [CI, 64% to 86%]; P < 0.01) prostate volume and serum prostate-specific antigen level (15% [CI, 6% to 24%]) with time on study, but DHT had no effect (P > 0.2). Dihydrotestosterone treatment decreased spinal BMD (1.4% [CI, 0.6% to 2.3%]; P < 0.001) at 24 months but not hip BMD (P > 0.2) and increased serum aminoterminal propeptide of type I procollagen in the second year of the study compared with placebo. Dihydrotestosterone increased serum DHT levels and its metabolites (5 alpha-androstane-3 alpha,17 beta-diol and 5 alpha-androstane-3 beta,17 beta-diol) and suppressed serum testosterone, estradiol, luteinizing hormone, and follicle-stimulating hormone levels. Dihydrotestosterone increased hemoglobin levels (7% [CI, 5% to 9%]), serum creatinine levels (9% [CI, 5% to 11%]), and lean mass (2.4% [CI, 1.6% to 3.1%) but decreased fat mass (5.2% [CI, 2.6% to 7.7%]) (P < 0.001 for all). Protocol-specific discontinuations due to DHT were asymptomatic increased hematocrit (n = 8), which resolved after stopping treatment, and increased prostate-specific antigen levels (n = 3; none with prostate cancer) in the DHT group. No serious adverse effects due to DHT occurred. Limitation: Negative findings on prostate growth cannot exclude adverse effects on the natural history of prostate cancer. Conclusion: Dihydrotestosterone treatment for 24 months has no beneficial or adverse effect on prostate growth but causes a decrease in spinal but not hip BMD. These findings have important implications for the wider use of nonsteroidal pure androgens in older men.