Cyproterone acetate (Cyp A) was administered to 35-day-old intact male rats parabiotically joined to hypophysectomized (H) males. Prostate weight in the latter was no higher than control values, indicating that the output of LH by the pituitary of the intact male was not increased, even though the effect of endogenous androgen was reduced as manifested by lowered sex accessory weights. Higher doses (2 mg/day) reduced prostate weight in the H partner, which could be accounted for by inhibition of LH output from the pituitary of the intact partner or /and exchange of Cyp A between partners. Both these mechanisms appeared operative by the results of 2 additional experiments. Castrated male parabionts were given 50 ng testosterone propionate daily and only one partner received Cyp A. Most of the activity of the anti-androgen was apparent with a dose of 100 μg. The material crossed the parabiotic union to inhibit prostate growth in the uninjected member when its co-twin received 1 mg or more per day. With a dose of 2 mg it was estimated that about 5% crossed into the non-injected partner. When given to immature females Cyp A (2 mg/day) inhibited ovulation but not follicular development or estrogen production. Pituitary LH was elevated in animals receiving Cyp A but 4.8 mg of pure cyproterone had no effect upon LH. The results demonstrate that 1) the parabiotic technique cannot be used for the study of gonadotropin changes associated with Cyp A, and 2) it inhibits the release of LH from the pituitary. These findings offer evidence that at least some of the anti-androgenic effects of Cyp A could be accounted for by its effect upon the pituitary. (Endocrinology 84: 421, 1969)
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Johnson et al. (1969) studied this question.