Origin of Functional Differences Between Male and Female Hypophyses. ∗

Abstract

Summary

Transplantation of testes of newborn males into the neck region of littermate females gives “takes” in 80% of the cases. In 48% the grafts do not interfere with normal endocrine or reproductive functions of the carrier, while in 32% the implanted testis assumes control of the sexual differentiation of the hypophysis. The male type hypophysis stimulates follicular development but not luteinization in the host ovary. These hosts start constant oestrus and maintain this condition after the removal of the testicular graft. It is concluded (1) that the cases with “constant oestrus” are those in which the implanted testis is sufficiently active to have a leading influence upon the hypophysis which responds with the male type of constant non-cyclic function; (2) that the hypophysis is permanently altered; (3) that the sex type of the hypophysis is secondary, depending upon the presence of differentiated sex glands.