Apomorphine-induced growth hormone response is attenuated by ethanol but not dextromethorphan

Background: Misuse of alcohol drinking is a major health problem. Alcohol decreases spontaneous growth hormone (GH) secretion, but the mechanism is unclear. The aim of this study was to test whether administration of alcohol (study 1) or a N-methyl D-aspartate (NMDA) receptor antagonist (study 2) attenuates the GH response to pharmacological dopaminergic stimulation. Methods: The 2-session repeated measures design was conducted at the endocrine laboratory at the Department of Psychiatry at the Free University Berlin. Twenty healthy Caucasian males aged 35 +/- 10 years without a history of alcohol use disorders were tested using the Apomorphine (APO) challenge test. In study 1, we injected APO (0.01 mg/kg s.c.) 1 hour after oral administration of 1 g/kg ethanol and placebo, respectively. In study 2, the APO challenge was conducted after 0.3 mg/kg dextromethorphan (DXM) and placebo. The main outcome measures were the peak serum GH concentration and area under the time/concentration curve up to 120 minutes after APO. The effects of ethanol and DXM were tested using the Wilcoxon signed-rank tests. Results: Compared with placebo, alcohol significantly decreased the APO-induced GH release (mean and SEM peak GH concentration 19.9 +/- 3.2 vs 6.2 +/- 1.9 ng/mL, p = 0.002). Dextromethorphan did not change APO-induced GH response (22.5 +/- 5.4 vs 21.0 +/- 5.8 ng/mL, p = 0.105). Conclusion: A single intermediate alcohol dose markedly reduces GH response to dopaminergic stimulation. Although alcohol is thought to stimulate dopaminergic function in certain pathways, but not necessarily in the hypothalamus, our results are in line with the alcohol effect on baseline GH secretion. Growth hormone suppression appears not to be mediated by ethanol's NMDA-antagonistic properties.