What Are Endorphins?

Learn About Endorphins and Their Impact on the Body

Exercise can cause a release of endorphins.
Exercise can cause a release of endorphins.. Peopleimages/Getty Images

Endorphins are often called the body's natural pain relievers. Endorphins are biochemical substances made by the body that reduce pain and bring about a feeling of euphoria and well-being.

Classification of Endorphins

Endorphins are classified as "endogenous opioid polypeptides" and they are thought to be produced by the pituitary gland and hypothalamus during strenuous exercise, and in response to pain, excitement and other stress stimulus.

Once produced, endorphins are distributed throughout the nervous system where they interact with the opiate receptors to reduce our perception of pain. These natural pain relievers not only reduce the perception of pain, but they are also linked with an increased sense of euphoria and well-being.

History of Endorphins

Endorphins were first discovered in 1974 by two separate groups of independent investigators. Endorphins were discovered by utilizing and studying the brains of animals. Scientists John Hughes and Hans Kosterliltz, both of Scotland, first identified and isolated endorphins from the brain of a pig. Simultaneously, Rabi Simantou and Soloman Snyder, both of the United States, identified endorphins in a calf brain. It was also discovered that the human body, as well as the body of many animals, is capable of producing morphine itself.

The results of this varied research enabled neuroscientists to determine that the human brain contains endorphins to limit pain, which the pituitary releases when the body is under extreme stress, or feeling extreme pain.

These endorphins interact with receptors to reduce the overall perception of pain. The effects of this process are mimicked, and thus similar to the use of a drug such as morphine. Thus, if an artificial painkiller such as morphine is introduced into the body, hopefully by a doctor, it has an effect on the naturally occurring endorphins.

As such a painkiller is introduced, it occupies more of the brain’s pain receptors. The body senses this, and in return, less naturally occurring pain reducers are produced. This is a balancing technique by the body. However, when the artificial source is removed, many pain receptors become empty. This causes a craving for endorphins, often in the form of narcotics, and this is how addiction can begin.

The Runner’s High

For certain individuals, running an extremely long distance can cause a sensation, and a sense of euphoria that is compared to the high offered by drugs. The reported sensations of this runner’s high include: feelings of extreme peace, a sensation of floating, bliss, euphoria, and increased pain tolerance.

This runner’s high is credited to an increased level of endorphins in the brain. Endorphins are consistently released to the body as an individual runs, and eventually this surge in endorphins in the brain leads to the feelings of euphoria.


Boecker, H., Sprenger, T., Spilker, M.E., Henriksen, G., Koppenhoefer, M., Wagner, K.J., Valet, M., Berthele, A., Tolle, T.R. (2008). The Runner's High: Opioidergic Mechanisms in the Human Brain. Cerebral Cortex DOI: 10.1093/cercor/bhn013

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