Effects of a dopamine antagonist on the release of gonadotropin and prolactin in normal women and women with hyperprolactinemic anovulation.

Administration of a dopamine (DA) antagonist, metoclopramide (MCP) resulted in dose-related acute increments of circulating levels of LH and FSH in patients with hyperprolactinemic anovulation due to pituitary microadenoma but not in normal cycling women during the early follicular phase. Concomitant PRL responses to MCP in hyperprolactinemic patients were 1/10 those observed in the cycling women. These findings suggest a relative DA excess at the hypothalamic LRF neurons and a relative DA deficiency at the adenoma lactotroph of hyperprolactinemic patients as compared to cycling women.