Cortisol suppresses the LH, but not the FSH, response to gonadotropin-releasing hormone after orchidectomy.

Castration leads to a rapid increase in LH and FSH secretion, and exogenous gonadotropin-releasing hormone (GnRH) elicits supernormal secretion of LH and FSH after orchidectomy. Superimposition of adrenalectomy or pretreatment with cortisol prevents the acute castration-induced LH and FSH response seen within 24 h. The gonadotropin response to exogenous GnRH is not suppressed by adrenalectomy, indicating that adrenalectomy acts by preventing hypothalamic GnRH secretion and not by diminishing pituitary responsiveness to GnRH. Cortisol treatment severely reduces the response of LH to injected GnRH after castration, suggesting that cortisol suppression is at the pituitary level. Surprisingly, FSH secretory response to GnRH after orchidectomy is not suppressed by cortisol treatment, indicating a striking point of separate regulation of the two gonadotropins.