GLOSSARY

Endorphins are a group of endogenous opioid peptides made in the pituitary and brain. By binding to opioid receptors (especially μ), they reduce pain and create feelings of calm and well-being. The name comes from “endogenous morphine”.

Production and Release

The most important type, beta-endorphin, is made in the anterior pituitary together with ACTH from the shared precursor POMC. It is therefore released together with ACTH during stress, pain and intense exercise. The endogenous opioid family also includes enkephalins and dynorphins.

Effects

• Pain relief: blocks transmission of pain signals in the spinal cord and brain.
• Mood: feelings of euphoria and reduced anxiety.
• Other effects: influences hormone release, breathing and the immune system.

Scientific Note

The popular belief that the “runner’s high