Gonad Hormones and Sex Differentiation

Abstract

This lecture represents an attempt critically to review and evaluate various facts and opinions that have a bearing on the problem of the role of sex hormones in sexual differentiation in the vertebrates. Such evidence has been considered as may be available from a) the use of living tissues as sources of hormones, or as responding structures to possible embryonic gonad hormones, b) the utilization of chemical hormones to influence the development of the reproductive tract in various vertebrates from fish to mammals, and c) the effects of early gonadectomies[long dash]which have been extended on pouch young marsupials to periods in development only slightly older than the indifferent sexual stage. The author supports the thesis that differentiation of the reproductive system rests upon the genetic sex-determining factors, and does not involve secretion by the developing gonad. Whereas embryonic Mullerian and Wolffian ducts are peculiarly responsive to sex hormones, even at early stages, the persistence of the proper duct and development of the proper accessory reproductive structures for the sex of the individual are not conditioned by gonadal secreted hormones. The evidence is quite convincing that the gonad not only does not secrete hormone during its early development but is actually incapable of secreting hormone until periods subsequent to well established o and o reproductive systems.