Effects of a prolactin- and adrenocorticotropin-secreting tumor on gonadotropin levels and accessory sex organ weights in adult male rats: a possible role of the adrenals.

The presence of the transplantable PRL- and ACTH-secreting tumor 7315a in intact male rats resulted in very high serum PRL levels, decreased levels of LH and FSH, and reduced weights of testes and accessory sex organs. In gonadectomized rats bearing a small testosterone-filled capsule, the tumor inhibited the postcastration rise in gonadotropins and reduced the weights of the prostate and seminal vesicles. However, after adrenalectomy of intact or gonadectomized male rats bearing a small testosterone-filled capsule, inhibitory effects of the tumor on serum gonadotropin levels or on reproductive organ weights were totally absent. These results show that in adrenalectomized male rats hyperprolactinemia in itself doses not affect gonadotropin secretion and the androgenic action of testosterone. Rather, the tumor might exert a gonadotropin inhibitory action through elevated levels of PRL combined with progesterone, which is secreted by the ACTH-stimulated adrenal.