MODULATION OF PITUITARY RESPONSIVENESS TO EXOGENOUS LHRH BY AN OESTROGENIC AND AN ANTI‐OESTROGENIC COMPOUND IN THE NORMAL MALE

Abstract

The effect of clomiphene (100 mg daily for 10 days) and ethinyl estradiol (100 .mu.g daily for 10 days) on the gonadotropin response to synthetic luteinizing hormone releasing hormone (LHRH) was investigated in 2 groups of 5 normal males. A 3rd group of 5 men served as control group. LHRH, 25 .mu.g, was injected i.v. on days 0, 4, 7 and 10 and the response of serum LH (luteinizing hormone) and FSH (follicle stimulating hormone) was monitored by radioimmunoassay. In contrast to the wide inter-individual variation of the response pattern, the intraindividual variation of the response to LHRH in the control group was small. Clomiphene induced a significant elevation of the baseline levels of LH and FSH after a few days of treatment; the pituitary responsiveness to LHRH, however, was significantly reduced. Estrogen treatment resulted in a uniform suppression of both basal gonadotropin levels and pituitary responsiveness. The decreased gonadotropin response to LHRH during clomiphene treatment is thought to be caused by a relative and temporary pituitary depletion of the releasable gonadotropin content. Although the suppression of LH and FSH response during estrogen treatment may point to a direct inhibitory effect of estrogen on pituitary gonadotropin release, an indirect hypothalamic pathway, through suppression of endogenous LHRH, cannot be ruled out.