The Effect of a 5α;-Reductase Inhibitor on Androgen Mediated Growth of the Dog Prostate*

Abstract

The administration of testosterone cypionate (0.4 mg/kg BW [body wt] .cntdot. day) to castrated male dogs caused a doubling of prostate wt within 4 wk an increase in the content of testosterone and dihydrotesterone in the prostate. When the 5.alpha.-reductase inhibitor 17-N,N-diethylcarbamoyl-4-methyl-4-aza-5.alpha.-androstan-3-one (3 mg/kg BW .cntdot. day) was administered simultaneously with testosterone cypionate, prostatic testosterone content increased from 0.5 .+-. 0.2 to 4.1 .+-. 1.3 ng/mg DNA, the increase in prostatic dihydrotestosterone content was prevented, and prostatic size decreased to half the starting weight. Apparently, dihydrotestosterone formation plays a role in prostatic growth.