Prostaglandins are a group of physiologically active lipid compounds that have various hormone-like effects in animals. Prostaglandins have been found in almost all tissues in humans and other animals. They are enzymatically derived from fatty acids. Each prostaglandin contains 20 carbon atoms, including a 5-carbon ring. They are a subclass of eicosanoids and of the prostanoid class of fatty acid derivatives.

Structural differences between prostaglandins explain their different biological activities. A given prostaglandin may have different and even opposite effects on different tissues in some cases. The ability of the same prostaglandin to stimulate a reaction in one tissue and inhibit the same reaction in another tissue is determined by the type of receptor the prostaglandin binds to. They act as autocrine or paracrine factors with their target cells present in the immediate vicinity of the site of their secretion. Prostaglandins differ from endocrine hormones in that they are not produced at one specific site but at many locations throughout the human body.

Prostaglandins are potent locally acting vasodilators and inhibit blood platelet aggregation. Through their role in vasodilation, prostaglandins are also involved in inflammation. They are synthesized in the walls of blood vessels and serve the physiological function of preventing the formation of unnecessary clots, as well as regulating the contraction of smooth muscle tissue. In contrast, thromboxanes (produced by platelet cells) are vasoconstrictors and facilitate platelet aggregation. Its name comes from its role in clot formation (thrombosis).

Specific prostaglandins are named with a letter (indicating the type of ring structure) followed by a number (indicating the number of double bonds in the hydrocarbon structure). For example, prostaglandin E1 is abbreviated PGE1 or PGE1, and prostaglandin I2 is abbreviated PGI2 or PGI2. The number is traditionally subdivided when the context allows it; But, as with many similar subscript-containing nomenclatures, the subscript is simply lost in many database fields that can store only plain text (such as PubMed bibliographic fields), and readers are accustomed to seeing and typing it. no subscript.