Leydig cell function in hyper- or hypoprolactinemic states in healthy men]

In the present investigation the function of the Leydig cells, as the response of gonadal steroids to the injections i.m. of 2000 UI of hCG, was studied in 11 normal men, before and after the induction of hyper or hypoprolactinemia with sulpiride and bromocriptine treatments respectively. The normal response to hCG, showed an increment of serum estradiol concentration 24 h and another of serum testosterone 72 h after the administration of the gonadotropin. The serum FSH concentration decreased during the test. An increase of serum LH levels was observed in the hypoprolactinemic state, but the increment of estradiol was lower after injection of hCG. On the other hand, the hyperprolactinemia induced a low basal level of testosterone with a higher response of this steroid to hCG. The results suggest that hyperprolactinemia interfers the estradiol synthesis by Leydig cells while the loss of the trophic effect of prolactin on gonadal steroidogenesis, as seen in hypoprolactinemia produces a decrease of basal testosterone levels without any alteration of the response of this steroid to hCG. We conclude that prolactin plays an important role in the steroidogenesis of Leydig cells in normal men.