THE INHIBITION OF GONADOTROPHIC HORMONE SECRETION BY PHYSIOLOGICAL DOSES OF ESTROGEN*

Abstract

WHEN an immature female rat is united in parabiosis with an ovariectomized littermate, the ovaries of the intact rat undergo hypertrophy (Kallas, 1930). This has been attributed to the hypersecretion of gonadotrophins by the pituitary of the castrated rat, the hormones of which pass directly via the blood to the intact partner where they stimulate the ovaries (Bunster and Meyer, 1938; Biddulph, Meyer and Gumbreck, 1940). It is believed that the gonadotrophin which increases in the ovariectomized female is largely follicle stimulating hormone (Greep, 1940; Biddulph and Meyer, 1946). Daily injections of small quantities of estrogen, or larger quantities of androgen, desoxycorticosterone acetate, or progresterone into the ovariectomized partner prevent the hypersecretion of the gonadotrophic hormones by the pituitary and the corresponding hypertrophy of the ovaries of the partner (Bunster and Meyer, 1933; Biddulph, Meyer and Gumbreck, 1940; Byrnes and Shipley, 1950).