The effect of a 5α-reductase inhibitor on androgen mediated growth of the dog prostate

The administration of testosterone cypionate (0.4 mg/kg BW day) to castrated male dogs caused a doubling of prostate weight within 4 weeks and an increase in the content of testosterone and dihydrotestosterone in the prostate. When the 5α-reductase inhibitor 17-N, N-diethylcarbamoyl-4-methyl-4-aza-5α-androstan-3-one (3 mg/kg BW-day) was administeredsimultaneously 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. These results suggest that dihydrotestosterone formation plays a role in prostatic growth.