Different effects of naloxone on the growth hormone response to melatonin and pyridostigmine in normal men

Coiro, V.; Volpi, R.; Capretti, L.; Giuliani, N.; Caffarri, G.; Colla, R.; Marchesi, C.; Chiodera, P.

« Previous Next »Metabolism - Clinical and Experimental
Volume 47, Issue 7 , Pages 814-816, July 1998

Different effects of naloxone on the growth hormone response to melatonin and pyridostigmine in normal men☆

V. Coiro
- Address reprint requests to Vittorio Coiro, MD, Istituto di Clinica Medica Generale e Terapia Medica, Università di Parma, Via Gramsci 14, 43100 Parma, Italy.
- Department of Internal Medicine, Institute of Psychiatry, School of Medicine, University of Parma, Parma, Italy
- Endocrine Unit, Hospital of Codogno, Codogno, Italy
- Radioimmunoassay Laboratory, Hospital of Guastalla, Guastalla, Italy
R. Volpi
- Department of Internal Medicine, Institute of Psychiatry, School of Medicine, University of Parma, Parma, Italy
- Endocrine Unit, Hospital of Codogno, Codogno, Italy
- Radioimmunoassay Laboratory, Hospital of Guastalla, Guastalla, Italy
L. Capretti
- Department of Internal Medicine, Institute of Psychiatry, School of Medicine, University of Parma, Parma, Italy
- Endocrine Unit, Hospital of Codogno, Codogno, Italy
- Radioimmunoassay Laboratory, Hospital of Guastalla, Guastalla, Italy
N. Giuliani
- Department of Internal Medicine, Institute of Psychiatry, School of Medicine, University of Parma, Parma, Italy
- Endocrine Unit, Hospital of Codogno, Codogno, Italy
- Radioimmunoassay Laboratory, Hospital of Guastalla, Guastalla, Italy
G. Caffarri
- Department of Internal Medicine, Institute of Psychiatry, School of Medicine, University of Parma, Parma, Italy
- Endocrine Unit, Hospital of Codogno, Codogno, Italy
- Radioimmunoassay Laboratory, Hospital of Guastalla, Guastalla, Italy
R. Colla
- Department of Internal Medicine, Institute of Psychiatry, School of Medicine, University of Parma, Parma, Italy
- Endocrine Unit, Hospital of Codogno, Codogno, Italy
- Radioimmunoassay Laboratory, Hospital of Guastalla, Guastalla, Italy
C. Marchesi
- Department of Internal Medicine, Institute of Psychiatry, School of Medicine, University of Parma, Parma, Italy
- Endocrine Unit, Hospital of Codogno, Codogno, Italy
- Radioimmunoassay Laboratory, Hospital of Guastalla, Guastalla, Italy
P. Chiodera
- Department of Internal Medicine, Institute of Psychiatry, School of Medicine, University of Parma, Parma, Italy
- Endocrine Unit, Hospital of Codogno, Codogno, Italy
- Radioimmunoassay Laboratory, Hospital of Guastalla, Guastalla, Italy

Received 9 August 1997; accepted 2 January 1998.

Abstract

The effect of melatonin (MEL) (12 mg orally), pyridostigmine (60 mg orally), the combination of MEL and pyridostigmine, or placebo on growth hormone (GH) secretion was tested in seven normal men. In addition, MEL tests and pyridostigmine tests were repeated after pretreatment with naloxone (1.2-mg bolus followed by intravenous [IV] infusion of 1.6 mg/h for 3 hours). Serum GH levels increased fivefold after MEL and sixfold after pyridostigmine administration. The concomitant administration of MEL did not change the GH response to pyridostigmine. In the presence of naloxone, the GH response to MEL was completely abolished, whereas naloxone did not modify the pyridostigmine-induced GH increase. These data suggest that MEL and pyridostigmine stimulate GH secretion through a common mechanism, which is probably represented by the inhibition of somatostatin activity. However, in contrast to pyridostigmine, the action of MEL appears to be exerted through a naloxone-sensitive opioid mediation.

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