Functions of the hypophysis-gonad and hypophysis-adrenal cortex systems during repeated administration of gonadotropin-releasing hormone in the postnatal period.

The effects of multiple doses of gonadotropin-releasing hormone (luliberin, LH-RH) on the functional activity of the hypophysis--gonad and hypophysis--adrenal cortex systems were studied in young hamadril baboons of different ages. After six doses (given on alternate days) of LH-RH, radioimmunoassays were used to determine blood concentrations of testosterone, dihydrotestosterone, cortisol, 11-deoxycortisol, and luteinizing hormone. A reduction in the stimulatory effect of luliberin on the luteinizing hormone level in male hamadril baboons aged one year was seen after repeated doses. There was no tendency for the stimulatory effect of LH-RH on the accompanying increase in the testosterone level to decrease. Doses of LH-RH did not alter blood cortisol levels in animals aged two years, but led to increases in cortisol in one-year-old animals. Repeated doses of LH-RH to young male hamadril baboons produced changes in adrenal steroidogenesis, with reductions in the blood corticosterone, 11-deoxycortisol, and dihydrotestosterone levels.