Specific control of follicle stimulating hormone in the male: postulated site of action of inhibin.

Serum luteinizing and follicle stimulating hormone concentrations were related to gonadal function, as reflected by sperm count and serum testosterone concentrations, in a group of men studied over 10 years after surgical correction of bilateral cryptorchidism in childhood. The results indicated that while all degrees of gonadal function occurred in these patients, the main adverse effect of cryptorchidism was on spermatogenesis. In some of the patients with oligospermia and normal Leydig cell function there was an isolated increase of basal serum FSH concentrations, suggesting a specific impairment of the testicular production of 'inhibin'. Gonadotrophin releasing hormone (LHRH) tests in these patients were compared to those in patients with normal basal gonadotrophins and to those with elevated basal LH and FSH concentrations. A selective exaggeration of the FSH response to exogenous LHRH in the group of patients with a monotropic elevation of FSH concentrations suggests that 'inhibin' modulates the secretion of FSH by an action on the pituitary rather than by modifying endogenous LHRH production by the hypothalamus.