Effect of the Urinary Gonadotrophin Inhibitor on Endogenous and Exogenous Gonadotrophin

Abstract

SINCE the discovery of a gonadotrophin inhibitor in urinaiy extracts from children¹ and adults², there has been some controversy as to its mode of action. Because a constituent of human chorionic gonadotrophin (HCG), N-acetyl-D-neuraminic acid, reduced the uterine weight response to HCG, it was suggested that the inhibitor competes with the gonadotrophin for the site of hormone action³. It has also been postulated that the inhibitor suppresses secretion of endogenous gonadotrophin. This hypothesis was based on the similarity between the increased doses of gonadotrophins required for the production of a response in hypophysectomized animals compared with those given an inhibitor⁴. The possibility that the urinary inhibitor is an antagonistic substance which combines with HCG without affecting the pituitary–ovarian axis of the assay animal has also been considered⁵. I report here the effect of the urinary inhibitor on the pituitary content of gonadotrophin. Possible direct antagonism of HCG by the inhibitor has also been tested in vitro and in vivo.