The Correlationship between Basal Prolactin Levels and the Suppressive Effect of CB-154 or L-DOPA on GH Release in Acromegalic Patients

Abstract

It has been reported that the plasma growth hormone (GH) and prolactin (PRL) levels in acromegalic patients were suppressed after intensive administration of dopaminergic drugs, but we found that the plasma GH levels in some acromegalic patients were not suppressed. Plasma GH and PRL levels after a single oral administration of CB-154 (2.5mg) and L-DOPA (1g) were measured in 18 active acromegalic patients with and without galactorrhea. 1. The mean plasma GH levels after the administration were clearly suppressed in 8 patients with galactorrhea, while they were not suppressed in 10 patients without galactorrhea. These drugs were more effective in suppressing plasma GH levels in acromegalic patients with galactorrhea and hyperprolactinemia. 2. We calculated the responsiveness of the plasma GH level as follows: GH responsiveness (%) = (mean plasma GH level after the administration of CB-154 or L-DOPA)/ (basal GH level) x 100. The basal plasma PRL levels were inversely correlated with GH responsiveness (CB-154: r=-0.690, p less than 0.01. L-DOPA: r=-0.541, p less than 0.05). It was found that the effect of dopaminergic drugs on plasma GH levels was closely correlated with basal PRL levels in acromegalic patients. This implies that the chronic administration of CB-154 may be effective in acromegalic patients with galactorrhea and hyperprolactinemia.