Released when the body encounters stress or pain, endorphins are a natural brain chemical that can provide a "RUSH" of pleasure similar to that experienced with opinoid drug. Endorphin rushes are often reported by athletes after long, intense exercise sessions or in the wake of a physical injury.
The discovery of endorphins dates to the 1970s, when researchers were puzzled to discover that the brain had a special set of receptors that responded to opiate drugs like morphine. They thought it was odd that brains from all over the world were equipped to deal with a drug originally found only in the Middle East.
The existence of the receptors provided a clue that the body manufactured its own natural pain-killers. These chemicals, sometimes known as endogenous opioids, were soon discovered in the body.
Unlike opioids, the body's natural endorphins are not addicting...at least not physically. The chemicals are short-lived and disappear before the body can develop any form of dependency on them. Additionally, people feel no withdrawal symptoms when endorphins aren't produced.
Endorphins also stimulate the immune system by activating natural killer cells in the blood and postpone the effects of aging.
There are four different types of endorphins...alpha, beta, gamma, and sigma.