NCIt definition : An endogenous opioid-like substance found in the hypothalamus and pituitary gland
that produces a sense of well-being, euphoria, and can reduce physical and emotional
pain.;
Alternative definition : NCI-GLOSS: A substance produced in the brain, especially in the pituitary gland, that
blocks the sensation of pain. It is produced in response to pain, exercise, and other
forms of stress. It is a type of polypeptide hormone.;