A defect in catecholamine neurons in patients with prolactin-secreting pituitary adenoma.

Although basal plasma concentrations of dopamine, noradrenaline, and adrenaline in patients with prolactin-secreting pituitary adenoma are normal, responses to oral bromocriptine are not. 1 and 2 h after bromocriptine, plasma concentrations of these three catecholamines are decreased in normal men but not in patients with hyperprolactinaemia secondary to prolactin-secreting pituitary adenoma or in normoprolactinaemic patients in whom a pituitary adenoma has been removed. Patients with prolactin-secreting pituitary adenoma probably have a defect in the regulation of brain catecholamine metabolism.