Evidence for increased dopaminergic inhibition of secretion of thyroid-stimulating hormone in hyperprolactinemic patients with pituitary microadenoma.

The administration of a dopamine-receptor antagonist, metoclopramide (10 mg, intravenous bolus), elicited a significant increase in the circulating concentration of thyroid-stimulating hormone (TSH) which was substantially greater for hyperprolactinemic patients with pituitary microadenoma than for normal women during the early follicular phase of the cycle. This study provides evidence of an inhibitory role of hypothalamic dopamine in the regulation of secretion of TSH and suggests an increased dopaminergic inhibition of secretion of TSH in these patients with prolactin-secreting tumors.