This review article discusses the biochemical mechanisms of action of eicosanoids, which are oxygenated 20-carbon fatty acids derived from arachidonic acid. Eicosanoids include prostaglandins, leukotrienes, and hydroxy fatty acids, and are synthesized through cyclo-oxygenase and lipoxygenase pathways. Prostaglandins are formed via the cyclo-oxygenase pathway, while leukotrienes and related hydroxy fatty acids are formed via the lipoxygenase pathway. Eicosanoids play a crucial role in various physiological processes, including cardiovascular disease, osteoporosis, and arthritis. The article explains that eicosanoids act through G protein-coupled receptors, which are involved in the regulation of cellular responses. Prostanoids, such as prostaglandins and thromboxanes, are synthesized from arachidonic acid, which is released from glycerophospholipids in response to various stimuli. The synthesis of prostaglandins involves the enzyme PGG/H synthase, which is inhibited by aspirin and other nonsteroidal anti-inflammatory drugs. Leukotrienes are formed via the lipoxygenase pathway, and their synthesis is influenced by various factors, including the presence of specific enzymes and the availability of arachidonic acid. The article also discusses the role of eicosanoids in the regulation of water reabsorption in the kidney, highlighting the importance of prostaglandins in this process. Overall, the review emphasizes the biochemical mechanisms by which eicosanoids exert their effects, including their interaction with G protein-coupled receptors and their role in various physiological processes. The article concludes that eicosanoids are local hormones that play a critical role in the regulation of cellular responses and physiological functions.This review article discusses the biochemical mechanisms of action of eicosanoids, which are oxygenated 20-carbon fatty acids derived from arachidonic acid. Eicosanoids include prostaglandins, leukotrienes, and hydroxy fatty acids, and are synthesized through cyclo-oxygenase and lipoxygenase pathways. Prostaglandins are formed via the cyclo-oxygenase pathway, while leukotrienes and related hydroxy fatty acids are formed via the lipoxygenase pathway. Eicosanoids play a crucial role in various physiological processes, including cardiovascular disease, osteoporosis, and arthritis. The article explains that eicosanoids act through G protein-coupled receptors, which are involved in the regulation of cellular responses. Prostanoids, such as prostaglandins and thromboxanes, are synthesized from arachidonic acid, which is released from glycerophospholipids in response to various stimuli. The synthesis of prostaglandins involves the enzyme PGG/H synthase, which is inhibited by aspirin and other nonsteroidal anti-inflammatory drugs. Leukotrienes are formed via the lipoxygenase pathway, and their synthesis is influenced by various factors, including the presence of specific enzymes and the availability of arachidonic acid. The article also discusses the role of eicosanoids in the regulation of water reabsorption in the kidney, highlighting the importance of prostaglandins in this process. Overall, the review emphasizes the biochemical mechanisms by which eicosanoids exert their effects, including their interaction with G protein-coupled receptors and their role in various physiological processes. The article concludes that eicosanoids are local hormones that play a critical role in the regulation of cellular responses and physiological functions.