Ovarian-Dependent Development of a Stimulatory Effect of 5α-Dihydrotestosterone on Serum Follicle Stimulating Hormone in the Ovariectomized Rat1, 2

Abstract

The data presented here indicate that s.c. 5.alpha.-dihydrotestosterone (DHT) implants produce a biphasic effect on serum FSH [follicle stimulating hormone], an initial elevation through about 48 h followed by a decline, in rats ovariectomized as adults. Only the suppressive effects of DHT were observed in orchidectomized rats and the stimulatory effect of DHT in ovariectomized rats was not shared by testosterone. In another study, in which rats were gonadectomized at various ages, several days of DHT treatment suppressed serum FSH levels if ovariectomies were performed on or before Day 8 of postnatal life, whereas serum FSH was suppressed in orchidectomized rats by DHT regardless of the age at which orchidectomies were performed. Other results showed that the initial stimulatory effect of DHT on serum FSH in ovariectomized rats was observed if the rats were ovariectomized on Day 9 or later. The development of mechanism responsible for a DHT-induced elevation of serum FSH in ovariectomized rats may be dependent upon differentiation of the ovarian-brain-pituitary system and occurs during the 2nd postnatal week.