Feedback control of gonadotropin secretion in mammalian and human males: effects of gonadotropin receptor blockers.

Abstract

Non-steroidal antiandrogens (NAA), flutamide and hydroxy-flutamide were used to study involvement of androgenic receptors in feedback control of gonadotropin secretion in males. In castrated animals these blockers inhibited the uptake of tritiated testosterone (T) by the hypothalamus and adenohypophysis. In male rats with intact gonads the NAA were found to reduce inhibitory effects of circulating endogenous androgens on the hypothalamus and pituitary gland which resulted in the increase of plasma LH, FSH and T levels, enhanced pituitary sensitivity to intravenously injected LHRH, increased activity of testicular steroid-delta 5-3 beta-ol-dehydrogenase. Endocrine response appeared the most pronounced in rats and was less marked in other animals species, and also in humans. No response was revealed in hypophysectomized male rats. Deafferentation of mediobasal hypothalamus by Halász knife had no impact on increased plasma T level following exposure to NAA. Furthermore, electrolytic destruction of arcuate nucleus and median eminence prevented or diminished significantly stimulation of LH, FSH and T secretion in NAA treated male rats. The results of this study suggest that androgenic receptors of mediobasal hypothalamus and pituitary gland are involved in control of gonadotropin secretion by circulating male sex hormones.