Effects of naloxone on prolactin, growth hormone and cortisol response to insulin hypoglycemia in obese subjects.

Recent studies suggest that opioid peptides may influence the secretion of pituitary gland hormones. Since obese patients often show impaired growth hormone (GH), prolactin (PRL) and cortisol responses to stimuli and raised beta endorphin levels, the opioid regulation of such hormone secretion could be different from that in normal weight subjects. In order to verify this hypothesis we studied the effect of iv naloxone, an opiate receptor antagonist, on GH, PRL and cortisol response to insulin-induced hypoglycemia in 9 obese female subjects. Seven normal weight females were used as control group. A control test using saline showed that the PRL and GH responses to insulin stress were impaired in obese subjects, whereas no difference was seen in the cortisol response. Naloxone did not modify the PRL and GH response but provoked a rise in the cortisol response in both obese and normal weight subjects. These findings suggest that while the opioid peptides do not play an important role in regulating the GH and PRL response to insulin hypoglycemia, they influence the cortisol response. In obese patients the impairment in GH and PRL response to stimuli cannot be related to alterations in opioid peptide regulation.