Maintenance and Restoration of Spermatogenesis in Hypophysectomized Rhesus Monkeys by Androgen Administration *

Experimental work on the maintenance and the restoration of spermatogenesis after hypophysectomy by -the administration of androgens has been limited to the smaller laboratory animals (rats, mice, guinea-pigs, rabbits, ground-squirrels, and pigeons). Rats have been the animals most commonly used. In them the period of time during which spermatogenesis has been maintained following hypophysectomy has been extended from 20 days, as first reported by Walsh, Cuyler, and McCullagh,9 to 178 days (Nelson6). It has been shown (Nelson7) that sperm formation can be re-initiated in hypophysectomized rats by androgen administration after a postoperative lapse of 20 days. Dvoskin3 has shown that the relatively large daily dosages which have been required to maintain spermatogenesis after hypophysectomy are due to the method of administration. He found that an amount of hormone too small to be effective if injected intramuscularly would maintain spermatogenesis if implanted as a pellet directly into a testis. By reducing the amount absorbed, spermatogenesis was maintained in the testis into which the pellet was implanted, whereas the contralateral one underwent involution. He also secured evidence that within a testis the seminiferous tubules in the neighborhood of the pellet were better maintained than were those more remote from the pellet. A number of years ago the writer began experiments in adult male rhesus monkeys to determine: (1) if androgen administration would maintain spermatogenesis after hypophysectomy, and (2) if androgen administration would restore spermatogenesis after the testes had undergone involution following ablation of the hypophysis. It seemed of interest to secure information on these questions, for, as has been pointed out (Smith8), the involution of the testes of monkeys after hypophysectomy results in a structural condition which is quite different from that of rats but which is similar to or identical with that in man. In monkeys the cellular constituents of