Effect of domperidone on prolactin (PRL)and thyrotrophin (TSH) secretion

Domperidone, a novel dopamine receptor blocking substance, unable to cross the blood brain barrier, was tested in twenty euthyroid volunteers of both sexes and in seven women with autonomous nodular goiter. Oral administration of 20 mg domperidone was followed by marked increase in serum PRL in all subjects; the response, being significantly greater in women as compared to men, was maintained in patients with autonomous goiter. The PRL response after oral domperidone was significantly greater than after 200 micrograms TRH intravenously. The PRL response obtained with oral domperidone followed by 200 microgram TRH i.v. was similar to the response obtained with domperidone alone before TRH administration. In euthyroid men the TSH response to 200 microgram TRH administered intravenously 120 min after oral domperidone was significantly greater than in a control TRH test. The data of the present study suggest that dopamine blockade at pituitary (or median eminence) level is able to stimulate maximally the lactotrophs and emphasize the important role of the dopaminergic system in the interrelated regulation of TSH and PRL secretion at the pituitary level.