THE ACTION OF ESTROGEN AND PROGESTERONE ON THE GONADOTROPIN CONTENT OF THE PITUITARY OF THE MONKEY (MACACA MULATTA)*

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Abstract
IN a recent review, Greep and Jones (1) indicated that though a great deal is known concerning the action. of the pituitary hormone on the target organs, very little is known “as to what the secretory products of the target organs do to the pituitary gland.” It is universally accepted now that the ovary is under the control of three gonadotropins from the anteriorpituitary. These are the follicle-stimulating hormone (FSH), the luteinizing hormone (LH) and the luteotropic hormone (LTH). There is no doubt that the gonadotropins are in turn regulated by the sex steroids but their specific role in regulating the hypophysis is still questionable. A marked increase in the gonadotropin concentration of the hypophysis after castration has been demonstrated in the guinea pig (2), the rabbit(3) and the rat (4). In 1932, Zondek (5) reported an increase in the gonadotropin concentration of the urine of castrated men and women. The results obtained from treatment with estrogenic substances have been somewhat more controversial. Numerous investigators have indicated that estrogens stimulate the release of LH (6, 7, 8) while suppressing FSH production (9, 10, 4, 11). The injection of large doses of estrogen in the human causes a definite decrease in the excretion of gonadotropins (12), as well as a decrease in pituitary potency (13). On the other hand, moderate doses of estrogen do not lower the postmenopausal excretion of urinary gonadotropins in women (14) nor do they suppress urinary gonadotropins in castrated women (15). From these and other data, Junck, Heller and Nelson (16) concluded that moderate amounts of estrogen exert little inhibiting action on the pituitary gland but large “unphysiological” amounts of estrogen are potent inhibitors. In contradistinction to this, Greep and Jones (11) indicate that smaller amounts of estrogen will counteract the effect of castration on the gonad-stimulating potency of the pituitary gland. Byrnes and Meyer (17) have arrived at the same conclusion from experiments involving parabiosis.