Peptide directoryBrain, hypothalamus & pituitary

Beta-endorphin

The body’s own morphine, released with ACTH under stress.

Where it comes from

Made in
Pituitary corticotrophs (into blood) and POMC neurons of the arcuate nucleus and brainstem (into the brain)
Sent out by
Stress, pain, exercise, and sex, alongside ACTH
Acts on
  • Pain pathways of brain and spinal cord
  • Reward circuits
  • Immune cells
  • Hypothalamus (GnRH, temperature)

What it does

  • Dulls pain and lifts mood in the brain
  • Circulating beta-endorphin cannot cross the blood-brain barrier, so what the blood carries does not explain the runner’s high; endocannabinoids are the better candidate
  • Restrains the reproductive axis during stress

In medicine

  • No medicine; morphine and its relatives act on its receptor
  • Measured in research in pain, addiction and exercise

Beyond the body’s own use

  • Beta-endorphin was infused into the spinal fluid for cancer pain in small studies and was not pursued; no product exists
  • The “endorphin rush” of exercise does not survive testing: blocking opioid receptors with naltrexone left the euphoria and the calm after a run intact 1
  • In mice those same effects need cannabinoid receptors rather than opioid ones, which is why endocannabinoids are now the better-supported explanation 2
  • Claims about activities that “release endorphins” almost always rest on a rise in blood beta-endorphin, which does not reach the brain and says little about it

Sources

  1. Siebers et al., Exercise-induced euphoria and anxiolysis do not depend on endogenous opioids, Psychoneuroendocrinology 2021
  2. Fuss et al., A runner’s high depends on cannabinoid receptors in mice, Proceedings of the National Academy of Sciences 2015

This card describes what a medicine is for and what the evidence says; it recommends nothing. Talk to your clinician about anything you read here.