Changes in dihydrotestosterone metabolism and the development of benign prostatic hyperplasia in the aging beagle

Previous studies have demonstrated that the 2-3-fold abnormal elevation in prostatic dihydrotestosterone (DHT) content characteristically associated with canine benign prostatic hyperplasia (BPH) is due to a shift in the overall balance in the complex metabolism of DHT in the gland itself [1,2]. Since the incidence of canine BPH increases with host age [3], the question arises as to whether the characteristic shift in DHT metabolism is associated with the general process of aging or with the specific development of BPH. To resolve this issue, the activities of prostatic androgen metabolism were quantitatively assayed in prostatic tissue from a large series of age-matched normal and BPH dogs ranging in age from 0.7-9.0 years. These analyses revealed that, regardless of the age of the host, there is a consistent statistical increase in several of the activities which produce DHT (i.e. 5α-reductase, 3α-HSOR oxidase, and 17β-HSOR reductase) without a concomitant increase in any of the activities which remove this steroid in BPH as compared to age-matched normal prostatic tissue. These results suggest that in canine BPH tissue the characteristic changes in DHT metabolism which increase the tissue's ability for net formation of DHT are specifically associated with the development of BPH itself and not due simply to the general process of aging per se.