noun. Any of a group of peptide hormones that bind to opiate receptors and are found mainly in the brain. Endorphins reduce the sensation of pain and affect emotions.

noun. Any of a group of peptide hormones found in the brain that act as neurotransmitters and have properties similar to morphine.

noun. a neurochemical occurring naturally in the brain and having analgesic properties

"Therefore, although it was unknown to us at the time, the term endorphin was no longer useful as a generic term as I had proposed."

neurochemical  peptide  

beta endorphin  enkephalin  

amylin  combinationof  epigenetic  fast-twitch  graded-index