effects on penile reflexes and plasma hormones of hyperprolactinemia induced by mttw15 tumors the effects of severe hyperprolactinemia induced by mttw15 tumors prolactin and growthhormonesecreting pituitary adenoma on penile reflex activity and blood hormones were examined there was no significant adverse effect of hyperprolactinemia on penile reflexes at 7 14 or 21 days after tumor inoculation however a virtual elimination of penile reflex activity was observed 34 days after inoculation additionally significant decrements in serum testosterone and dihydrotestosterone and an elevation in progesterone were seen at this time concomittant with greatly increased prolactin levels the results suggest that erectile dysfunction may contribute to hyperprolactinemiainduced copulatory failure