Functional studies of dopamine control of prolactin secretion in normal women and women with hyperprolactinemic pituitary microadenoma.

Abstract

Functional studies of the dopamine-PRL system in the control of the secretory activity of the lactotrope were conducted in 8 normal cycling women during the early follicular phase of the cycle and in 14 hyperprolactinemic patients with pituitary microadenoma (prolactinoma). Dynamic changes in PRL release in response to dopamine infusion and a dopamine receptor antagonist [metoclopramide (MCP)], singly and in combination, were determined and compared between normal women and prolactinoma patients. Our data show that the degree of dopamine inhibition of PRL (via 4–h infusion) in prolactinoma patients was significantly greater in terms of both the absolute PRL decrement and the rate of PRL decline compared to normal women. A strong positive correlation (r = 0.964) was found between basal PRL levels and the magnitude of PRL decline during dopamine infusion. In contrast, the rebound PRL release above basal levels after dopamine withdrawal was significantly smaller in prolactinoma patients than in normal women....