Endogenous dopaminergic inhibition of aldosterone and prolactin secretion is apparently not increased in primary aldosteronism.

To examine the previous suggestion that the endogenous dopaminergic activity would be increased in patients with primary aldosteronism, dose-response curves of aldosterone and prolactin stimulation by the dopamine antagonist metoclopramide were established in a pilot study by injecting metoclopramide 1, 2.5, and 10 mg i.v. consecutively at hourly intervals to 6 patients with primary aldosteronism and 14 healthy volunteers. All three metoclopramide doses induced clear-cut rises in aldosterone levels both in patients with primary aldosteronism and healthy controls. Basal aldosterone concentration was higher in range in the patients but the dose-response curves were nearly parallel one with the other. Prolactin responsiveness was also very similar. Thus, the present findings do not support the hypothesis of an increase in endogenous dopaminergic activity in primary aldosteronism.