Opiate receptors and anterior pituitary hormone secretion in man. Effect of naloxone infusion

Abstract

The role of endogenous opioid receptors on anterior pituitary hormone secretion was evaluated by the administration of the opioid receptor antagonist naloxone. Naloxone infusion (8 mg i.v. followed by 4 mg/h for 3 h) did not alter basal growth hormone, prolactin and thyrotropin secretion but produced a significant rise in cortisol and gonadotropins in normal man. The infusion of the opiate antagonist appeared to increase the rate and amplitude of luteinizing hormone pulsatility. Naloxone pre-medication (10 mg i.v. 30 min before testing) did not alter the pituitary response to thyrotropin releasing hormone and luteinizing hormone releasing hormone-stimulation. Naloxone can modify basal anterior pituitary hormone secretion. This strongly suggests an endogenous opioid modulation of some of these hormones.