Altered metabolism of androgens in elderly men with benign prostatic hyperplasia

Kinetics of testosterone, dihydrotestosterone (DHT) and 5alpha-androstane-3alpha,17beta-diol (3alpha-diol) were studied in 7 elderly healthy men (ages 61 to 80 years) with benign prostatic hyperplasia (BPH). Clearance rates were determined by the constant infusion technique with labeled testosterone and DHT. Metabolic clearance rate (MCR), conversion ratio (CR), the transfer constants (rho) and production rates (PB) were calculated. Plasma androgens were measured by specific radioimmunoassay. Plasma testosterone was 516 +/- 314 (SD) ng/dl, plasma DHT was 74.6 +/- 19.6 (SD) ng/dl and plasma 3alpha-diol was 16.4 +/- 4.1 (SD) ng/dl. An elevated DHT level in elderly men with BPH wasconfirmed. MCRT was 620 +/- 65 (SD) liter/day and MCRDHT was 393 +/- 50 (SD) liter/day. Both MCRT and MCRDHT in elderly men were significantly lower than in young men. PBT was 3.2 +/- 2.1 (SD) mg/day and PBDHT was 291 +/- 87 (SD)migrogram/day. PBDHT was the same in elderly and young men. DHT production is maintained in elderly men despite reduction of testosterone production. From the data, it was claculated that in contrast to young men where greater than 80% of blood DHT is from secreted testosterone, over 50% in elderly men is derived from secretion or production of DHT by the testis or even more likely the prostate.