Canine benign prostatic hyperplasia (BPH) is associated with, if not actually induced by, an increased prostatic ability for the net formation of dihydrotestosterone (DHT). This conclusion is based upon the observation in this study that: 1) when spontaneous BPH develops in the beagle there is a concomitant increase in the potential capacity for prostatic tissue to metabolize steroids favoring the net formation of DHT; 2) there is a similar change in steroid metabolism in the prostate when BPH is experimentally induced in young beagles by the combined administration of exogenous androgens and estrogens; 3) various hormonal treatments of young intact or castrate dogs which did not increase the prostatic tissue's ability to produce DHT also did not induce a high incidence of experimental BPH; and 4) a highly significant linear correlation (r = 0.95) was observed between the size of the prostate gland and an increased prostatic ability for the net formation of DHT, as estimated by relative prostatic ix values which quantitatively reflect such increased metabolic activities. These overall alterations in prostatic steroid metabolism favor an increase in the net formation of DHT and may account for the well documented increase in DHT concentration associated with BPH in both dog and man. The enhancement of these events by estrogens could play a major role in the etiology of BPH.
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