Prl, TSH, GH and LH responses to metoclopramide and breast-feeding in normal and hyperprolactinaemic women

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Abstract
: In order to evaluate whether hyperprolactinaemic patients have an increased or decreased central dopaminergic tonus, we compared the serum Prl, TSH, GH and LH responses to metoclopramide (10 mg iv) and to breast-feeding in normal women (n = 8) and hyperprolactinaemic patients (n = 8). Prl increments to metoclopramide were significantly (P < 0.05) impaired in hyperprolactinaemic patients. Serum TSH increased significantly after metoclopramide both in normal and hyperprolactinaemic patients (P < 0.025), but no significant differences were found between the two groups regarding TSH, GH or LH levels. Hyperprolactinaemic pateints had no acute response to suckling while significant increments of Prl and GH (P < 0.025) occurred in normal women. Our data indicate that the central dopaminergic tonus was not altered in hyperprolactinaemic patients, but showed regulatory dysfunction of both Prl and GH. The concept of a dopaminergic inhibition of TSH secretion was confirmed.