Endorphins

A group of protein molecules produced in the body that relieve pain by activating opiate receptors in the nervous system. Endorphins have a similar chemical structure to the painrelieving drug morphine. In addition, endorphins are thought to be involved in the body’s response to stress, as well as in regulating intestinal contractions, determining mood, and controlling the release of certain hormones from the pituitary gland. (See also enkephalins.)