NALOXONE INFLUENCE ON THE GROWTH-HORMONE, PROLACTIN AND THYROTROPIN RESPONSE TO THYROTROPIN-RELEASING-HORMONE IN ACROMEGALIC PATIENTS

In order to gain insight into the neuroendocrine mechanism underlying the paradoxical GH response to TRH in acromegalic patients, we have in vestigated the effect of an infusion of Naloxone (Nal, 1.6 mg/hr for t wo hours), on a TRH test performed both in responder (n = 9) and non-r esponder (n = 5) acromegalic patients. The response of GH, PRL and TSH to TRH injection were evaluated. NAL did not exert significant variat ions in the GH response, even if different patterns of GH response dur ing NAL were observed in the group of TRH-responder patients. Similarl y, TRH-induced PRL response was not significantly affected by the infu sion of an opiate antagonist. On the contrary, a significant inhibitio n of the TSH response was observed in the group of TRH-responder patie nts (delta TSH after TRH 4.76 +/- 1.11 mu U/ml, after NAL +/- TRH 2.81 +/- 0.99 mu U/ml, p < 0.05). No significant effects were observed in the TRH nonresponder patients (delta TSH after TRH 4.58 +/- 1.44 mu U/ ml, after NAL +/- TRH 6.26 +/- 3.27 mu U/ml). The differences observed in the two groups of patients could be ascribed to a different endoge nous somatostatinergic tone and could fournish a prognostic indication in acromegalic patients.