Effects of naloxone on insulin-induced release of pituitary hormones

To evaluate the role of endogenous opiates on the regulation of the pituitary hormonal stress response, we have studied in six normal subjects the insulin-induced secretion of PRL, GH, and ACTH with and without naloxone, a specific opiate antagonist. During hypoglycemia, naloxone infusion reduced plasma PRL levels at 90 min, lowered the overall GH response, and enhanced that of ACTH. These observations suggest that endogenous opiates have a modulatory role in the stress-induced secretion of pituitary hormones.