[Peripheral effects of prolactin in reproductive function. I. Male reproductive function]

Prolactin plays a peripheral role in male reproductive function just as it does in female function. Prolactin, through the medium of immunocytochemistry acts on testicular steroidogenesis through prolactin receptors which are sited on the Leydig cells. It alters the number of LH receptors and therefore the sensitivity of the testis to central stimulation and equally interferes with androgen synthesis. In the areas of physiological concentration the principal effect seems to be to stimulate secretion of testosterone by keeping up the number of LH receptors; but when there is acute hyperprolactinaemia, testosterone secretion is lowered or perhaps not changed at all because of a "post-receptor effect", in spite of there being larger numbers of LH receptors. The direct effect of prolactin on spermatogenesis has not yet been worked out and the results that have been obtained are controversial. Prolactin exerts a direct stimulating effect on the growth of prostatic cells working synergistically with testosterone through specific prolactin receptors. It could play a role in certain cancers of the prostate.