A group of neuropeptide hormones (or neurotransmitters), found mainly in the brain, that bind to opiate receptors, and which have analgesic properties similar to morphine. Twenty different types of endorphins have been identified, but the three major ones are beta endorphins (composed of 31 amino acids) located chiefly in the pituitary gland, and enkephalins and dynorphins that are both distributed throughout the nervous system. It has been suggested that some individuals with autism have higher than normal concentrations of beta endorphins. Endorphins are considered to interact with opiate receptor neurons, but the mechanisms underlying this process are not fully understood. In addition to regulating somatic pain, endorphins are thought to be involved in feelings of euphoria, modulation of appetite, and the release of sex hormones. Prolonged aerobic exercise is claimed to increase the production and release of endorphins, thus giving rise to the euphoric state referred to as ‘runner’s high’. It is known that they inhibit the flow of dopamine, which results in a decrease of the number of receptors sensitive to dopamine, and thus the replacement of pain with feelings of pleasure.
See Amino acids, Autism, Dopamine, Hormones, Peptides