endorphin

American  

[en-dawr-fin] / ɛnˈdɔr fɪn /

noun

1. any of a group of peptides occurring in the brain and other tissues of vertebrates, and resembling opiates, that react with the brain's opiate receptors to raise the pain threshold.

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endorphin British  

/ ɛnˈdɔːfɪn /

noun

1. any of a class of polypeptides, including enkephalin, occurring naturally in the brain, that bind to pain receptors and so block pain sensation

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endorphin Scientific  

/ ĕn-dôr′fĭn /

1. Any of a group of peptide substances secreted by the anterior portion of the pituitary gland that inhibit the perception of painful stimuli. Endorphins act as neurotransmitters in the pain pathways of the brain and spinal cord. Narcotic drugs may stimulate the secretion of endorphins.

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Closer Look

Endorphins are long chains of amino acids, or polypeptides, that are able to bind to the neuroreceptors in the brain and are capable of relieving pain in a manner similar to that of morphine. There are three major types of endorphins: beta-endorphins are found almost entirely in the pituitary gland, while enkephalins and dynorphins are both distributed throughout the nervous system. Scientists had suspected that analgesic opiates, such as morphine and heroin, worked effectively against pain because the body had receptors that were activated by such drugs. They reasoned that these receptors probably existed because the body itself had natural painkilling compounds that also bonded to those receptors. When scientists in the 1970s isolated a biochemical from a pituitary gland hormone that showed analgesic properties, Choh Li, a chemist from Berkeley, California, named it endorphin, meaning “the morphine within.” Besides behaving as a pain reducer, endorphins are also thought to be connected to euphoric feelings, appetite modulation, and the release of sex hormones. Prolonged, continuous exercise contributes to an increased production of endorphins and, in some people, the subsequent “runner's high.”

Etymology

Origin of endorphin

1970–75; end(ogenous) (m)orphine, with -ine respelled as -in ²

Example Sentences

It may be a thrill show and a shallow endorphin rush, but the one thing that it isn’t is journalism, which we still happily criticize.

From Salon • Feb. 6, 2026

"The people you talk to, and laugh with, it leads to enhanced levels of endorphin uptake," says Prof Scott.

From BBC • Dec. 22, 2025

Zoe Giles, a 34-year-old mother of two in Kent, England, gets an endorphin rush each time a package arrives from Shein or Temu.

From The Wall Street Journal • Dec. 18, 2025

A mutation in a gene called pro-opiomelanocortin prevents the production of a hormone and a kind of endorphin, the absence of which acts as a starvation signal.

From Science Magazine • Mar. 8, 2024

I woke disoriented and crabby, without my customary morning jolt of endorphin.

From Down and Out in the Magic Kingdom by Doctorow, Cory