Treating healthy middle-aged men with dihydrotestosterone (DHT) for two years had no effect on prostate growth but resulted in an increased fall in spinal bone density in a controlled trial.

Benign prostatic hypertrophy (BPH) is common in elderly men and can cause significant morbidity, thus any intervention that might slow prostatic growth could reduce the personal and healthcare system costs associated with it. Previous work suggests that DHT administration might slow prostate growth. This study examined whether administration of pharmacological doses of DHT, a more potent (3x to 5x) testosterone metabolite produced naturally in humans by the enzyme 5-alpha reductase, would reduce prostatic growth in healthy middle-aged men. Participants were men aged 50 and above with no known prostate disease or other serious chronic medical condition. They were randomised to transdermal DHT 70mg as a gel daily or a matching placebo for two years. Primary outcome was prostate volume measured by ultrasonography; secondary outcomes included bone mineral density (BMD) at spine and hip, and body composition.

Of 309 men assessed for eligibility, 114 were randomised to the study (DHT n=56, placebo n=58); 33 withdrew during the course of the study, most often due to adverse events, and four (1 vs. 3) could not be included in the final analysis due to withdrawal of consent or protocol violation. Over the study period, there was an increase in total (29%; 95% CI, 23% to 34%) and central (75%; 95% CI, 64% to 86%; P < 0.01) prostate volume and in serum prostate-specific antigen (PSA) level (15%; 95% CI, 6% to 24%), but DHT had no significant effect (P > 0.2). Spinal BMD decreased by 1.4% at 24 months (95% CI, 0.6% to 2.3%; P < 0.001) but hip BMD did not alter significantly over this period (P > 0.2).

There were 18 withdrawals due to adverse events, 13 in the DHT group and 5 in the placebo-group: eight of those in the DHT group were for potentially drug-related adverse effects (polycythemia in 8 and raised PSA level in 3).

Based on their results, the authors conclude that 24 months treatment of healthy middle-aged men with DHT has no significant effect on prostate growth. It reduces BMD in the spine, but not the hip. They comment that their study adds to the knowledge on the actions of androgens in this age group.

An accompanying editorial discusses the study.