Neuroendocrine effects of endogenous opioid peptides in human subjects: a review

In the decade since the discovery of specific opioid receptors in the brain, there have been rapid advances in our understanding of the physiological and pathological roles of the endogenous opioid systems in humans. Endogenous opioid peptides have been demonstrated to play a role as modulators of a number of hormonal functions in humans. In particular they appear to inhibit luteinizing hormone and ACTH release, and the response of arginine vasopressin to osmotic stimuli. They appear to participate in the modulation of carbohydrate homeostasis. In pathophysiological states, they appear to play a role in the decreased pulsatile luteinizing hormone release seen in patients with prolactinomas. Circulating beta-endorphin appears to be an important regulator of immune function. Preliminary studies in humans have suggested a role for endogenous opioid peptides in appetite regulation. In the last few years, a few case reports have suggested the possibility of a series of syndromes due to endogenous opioid excess. Within the next decade, we can expect to see the routine use of opioid antagonists in a variety of pathophysiological states.