ANDROGEN METABOLISM IN MEN RECEIVING FINASTERIDE BEFORE PROSTATECTOMY

Oral administration of finasteride, a 5alpha-reductase inhibitor, affe cts intraprostatic androgens by suppressing dihydrotestosterone and in creasing testosterone. This study was designed to determine the correl ation of these effects of finasteride with changes in serum dihydrotes tosterone, testosterone and androstanediol glucuronide. In a double bl ind, placebo-controlled study, 27 men with symptomatic benign prostati c hyperplasia were treated with placebo or 1 or 5 mg. per day finaster ide for 6 to 8 weeks before transurethral resection of the prostate. T here was no significant change in serum testosterone in any group, or in serum dihydrotestosterone or androstanediol glucuronide in the plac ebo group. There was a decrease in serum dihydrotestosterone by 66 +/- 4% and 70 +/- 8% (p = 0.32), and of serum androstanediol glucuronide by 78 +/- 3% and 86 +/- 3% (p = 0.012) in the 1 and 5 mg. finasteride groups, respectively. Intraprostatic dihydrotestosterone in the placeb o group decreased from 18.6 +/- 1.4 nmol./kg. to 3.8 +/- 1.0 nmol./kg. and 1.7 +/- 0.7 nmol./kg. with 1 mg. and 5 mg. finasteride, respectiv ely (p = 0.049 between 1 mg. and 5 mg. finasteride). Intraprostatic te stosterone in the placebo group increased from 1.1 +/- 0.2 nmol./kg. t o 7.6 +/- 1.0 nmol./kg. and 8.3 +/- 0.7 nmol./kg. with 1 mg. and 5 mg. finasteride, respectively (no significant difference between 1 mg. an d 5 mg. finasteride). Serum and intraprostatic dihydrotestosterone cor related (p = 0.002). There was no correlation between intraprostatic d ihydrotestosterone and serum androstanediol glucuronide. We conclude t hat 5 mg. of finasteride cause greater inhibition of intraprostatic 5a lpha-reductase than 1 mg. and that serum dihydrotestosterone is a bett er marker of intraprostatic dihydrotestosterone than androstanediol gl ucuronide.