Failure of dopamine infusion to suppress the plasma prolactin response to sulpiride in normal and hyperprolactinemic subjects.

In eleven normal women dopamine infusion (5 microgram/Kg/min) significantly lowered plasma prolactin levels but failed to suppress the PRL response to sulpiride (10 or 100 mg i.v.), while the same dose of dopamine was effective in abolishing the PRL response to TRH (200 microgram i.v.). In four hyperprolactinemic women showing an impaired PRL response to sulpiride, dopamine infusion was effective both in lowering PRL circulating levels and in restoring an evident response to sulpiride. This finding suggests an impairment of endogenous dopamine activity in hyperprolactinemic amenorrhea.