Endorphins are among the brain chemicals known as neurotransmitters, which function to transmit electrical signals within the nervous system. Endorphins can be found in the pituitary gland, in other parts of the brain, or distributed throughout the nervous system.
In addition to decreased feelings of pain, secretion of endorphins leads to feelings of euphoria, modulation of appetite, release of sex hormones, and enhancement of the immune response. With high endorphin levels, we feel less pain and fewer negative effects of stress. Endorphins have been suggested as modulators of the so-called "runner's high" that athletes achieve with prolonged exercise.
While the role of endorphins as potential triggers of this euphoric response has been debated extensively by doctors and scientists, it is at least known that the body does produce endorphins in response to prolonged, continuous exercise.