endogenous
adjective
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When biologists need to make a distinction between things that are produced within a cell or organ and things that affect it from the outside, they use the terms endogenous and exogenous. It used to be thought, for instance, that mutations in cells always resulted from exogenous causes, until it was discovered that substances in the body, including those called oxidants, could cause them endogenously as well. "Circadian rhythms"—the regular cycles, roughly 24 hours in length, that plants, animals, and humans rely on to regulate their days—are endogenously generated and don't actually depend on the sun for their timing.
Examples of endogenous in a Sentence
Anjana Susarla, Forbes.com, 3 Sep. 2025
Under extreme stress, the fight-or-flight hormones aggressively trigger the endogenous opioid system, which greatly reduces the pain.
—Dr. Sanjay Gupta, CNN Money, 26 Aug. 2025
These compounds are typically synthesized from plant precursors, such as molecules derived from yams or soy, and formulated to mimic endogenous hormones.
—Jason Phillips, USA Today, 23 Aug. 2025
As Rosas-Vidal hinted at, endogenous cannabinoids or endocannabinoids are produced by the body to activate CB1 (cannabinoid receptor 1) receptors, the receptors that are also responsible for producing the psychoactive effects of cannabis.
—Paul McClure 24, New Atlas, 24 May 2025
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Cite this Entry
“Endogenous.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/endogenous. Accessed 9 Sep. 2025.
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endogenous
adjective
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