endorphin

Endorphin was coined in 1975 by combining 'endogenous' (produced within the body) and 'morphine' (the opiate painkiller). The word names what the molecule is: morphine that the body makes itself. Rabi Simantov and Solomon Snyder at Johns Hopkins, along with John Hughes and Hans Kosterlitz in Aberdeen, Scotland, independently discovered endogenous opioid peptides in the mid-1970s. Hughes and Kosterlitz initially called their discovery 'enkephalin' (in the brain). The broader class of such molecules became 'endorphins.'

The discovery emerged from a question: why does the brain have receptors for opium? Candace Pert and Snyder identified opioid receptors in the brain in 1973. Receptors exist because the body produces its own molecules to bind to them — evolution does not build locks without keys. The search for the body's own opiates led to endorphins, enkephalins, and dynorphins: three families of molecules that reduce pain, produce euphoria, and regulate stress.

The 'runner's high' — the euphoric sensation reported during prolonged exercise — became the most famous endorphin-associated phenomenon. The connection was proposed in the 1980s, and studies in 2008 using PET scans confirmed that endorphin levels rise in the brain after sustained running. The effect requires at least 20 to 30 minutes of moderate-to-intense exercise. Sprinters do not get runner's high. Distance runners do.

Endorphin has entered everyday language as a synonym for natural good feeling. Exercise releases endorphins. Laughter releases endorphins. Chocolate may release endorphins. Spicy food may release endorphins. The word has become a vague promise of well-being, detached from its precise pharmacological meaning. Your body does manufacture its own morphine. It does not do so every time you eat a candy bar.