What does eicosanoid mean?
An eicosanoid is any member of a family of biologically potent signalling molecules produced in the body from twenty-carbon polyunsaturated fatty acids — most famously arachidonic acid. The group includes prostaglandins, thromboxanes, and leukotrienes, each of which helps regulate processes such as inflammation, fever, pain, blood clotting, and smooth-muscle contraction. The name comes from the Greek word for twenty, reflecting the uniform carbon-chain length of the parent fatty acids. Eicosanoids are not stored but are synthesised on demand at the site where they act, which is why they are described as local mediators rather than hormones. The term belongs chiefly to biochemistry, medicine, and pharmacology: drugs like aspirin and ibuprofen exert their effects precisely by suppressing eicosanoid production. Understanding this word opens a window onto how the body generates both healing responses and the inflammation behind many common diseases.
nounAny of a group of biologically active signalling molecules derived from twenty-carbon polyunsaturated fatty acids such as arachidonic acid, including prostaglandins, thromboxanes, leukotrienes, and related compounds.
- Any of a class of signalling molecules derived from twenty-carbon polyunsaturated fatty acids that mediate inflammation, blood clotting, immune responses, and other local physiological processes.
"Aspirin relieves inflammation by blocking the enzymes that produce eicosanoids."
"Non-steroidal anti-inflammatory drugs work by inhibiting the cyclooxygenase enzymes responsible for eicosanoid synthesis."
"Leukotrienes, a subclass of eicosanoids, play a central role in the airway inflammation seen in asthma."
Standard regular plural; the plural is more common than the singular because the term usually refers to the class as a whole.
"Omega-3 fatty acids give rise to less inflammatory eicosanoids than omega-6 fatty acids do."
The 'eicosa' in eicosanoid simply means 'twenty' in Greek — every one of these powerful inflammation molecules is built on a chain of exactly twenty carbon atoms.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of eicosanoid
The word eicosanoid was coined in the twentieth century within biochemistry, combining the Greek 'eikosi' meaning 'twenty' with '-anoid', reflecting the twenty-carbon fatty-acid backbone common to all members of the class. The same Greek root for twenty appears in chemical terms such as eicosane, the saturated hydrocarbon with twenty carbon atoms. The suffix echoes terms like 'steroid' and 'alkanoid', marking the molecule's structural derivation from a defined parent skeleton.
Related word forms
How eicosanoid is actually used
A technical term used almost exclusively in biochemistry, pharmacology, and medicine; it is rare in everyday speech. It is nearly always used in scientific writing in its plural form or as an attributive modifier (as in 'eicosanoid pathway').
Easily confused with eicosanoid
Steroids are lipids derived from cholesterol with a four-ring structure and act largely as hormones, whereas eicosanoids are derived from twenty-carbon fatty acids and act mainly as local inflammatory mediators.