Selective inhibition of androstenedione-induced prostate growth in intact beagle dogs by a combined treatment with the antiandrogen cyproterone acetate and the aromatase inhibitor 1-methyl-androsta-1,4-diene-3,17-dione (1-methyl-ADD).

Interference with estrogenic and androgenic actions might result in an inhibitory effect of benign prostatic hyperplasia (BPH). In the present study the effects of the treatment of intact, adult beagle dogs with the antiandrogen cyproterone acetate (CPA) and the aromatase inhibitor 1-methyl-ADD either alone or in combination on androstenedione-induced prostate growth and on testes, epididymides, and the pituitary was investigated. 1-Methyl-ADD induced a marked counterregulatory increase in the serum testosterone and dihydrotestosterone (DHT) concentrations leading to hyperplasia of the glandular part of the prostate. However, the aromatase inhibitor antagonized the androstenedione-induced (estrogen-related) stimulation of the fibromuscular stroma of the prostate. CPA caused a complete atrophy of the prostate that was also present after treatment with both the aromatase inhibitor and CPA in spite of a striking elevation of the serum testosterone and DHT levels and in spite of the antagonization of the inhibition of testes and epididymal weight induced by androstenedione plus CPA. This indicates a selective inhibition of the prostate of intact beagle dogs treated with CPA and 1-methyl-ADD.