Endorphin

Endorphins are endogenous opioid neuropeptides produced by the central nervous system and the pituitary gland. They are most commonly associated with reduced pain and increased feelings of pleasure and euphoria, but they also exert control on the immune system, such as boosting the activity of natural killer cells.

Low dose naltrexone has been shown to increase the secretion of beta-endorphin.

Notable studies

 * 2016, Peripheral blood mononuclear cell beta-endorphin concentration is decreased in chronic fatigue syndrome and fibromyalgia but not in depression: preliminary report