endorphin

Etymology

Borrowed from French endorphine, from endo(gène) (“endogenous, produced within”) and morphine.

noun

1. (biochemistry) Any of a group of peptide hormones found in the mammalian brain that act as neurotransmitters and have properties similar to morphine.
   The explanation for the depression-reducing effects of exercise that clearly has been the most popular with the media is the endorphin hypothesis (see Hoffmann, 1997), which has also been discussed as a possible explanation in nearly every exercise-depression literature review. 2019, Curt L. Lox, Kathleen A. Martin Ginis, Heather L. Gainforth, Steven J. Petruzzello, The Psychology of Exercise: Integrating Theory and Practice, Routledge