13,14-dihydro PGE1 is a prostanoid. Prostanoids is a term that collectively describes prostaglandins, prostacyclines and thromboxanes. Prostanoids are a subclass of the lipid mediator group known as eicosanoids. They derive from C-20 polyunsaturated fatty acids, mainly dihomo-gamma-linoleic (20:3n-6), arachidonic (20:4n-6), and eicosapentaenoic (20:5n-3) acids, through the action of cyclooxygenases-1 and -2 (COX-1 and COX-2). The reaction product of COX is the unstable endoperoxide prostaglandin H (PGH) that is further transformed into the individual prostanoids by a series of specific prostanoid synthases. Prostanoids are local-acting mediators formed and inactivated within the same or neighbouring cells prior to their release into circulation as inactive metabolites (15-keto- and 13,14-dihydroketo metabolites). Non-enzymatic peroxidation of arachidonic acid and other fatty acids in vivo can result in prostaglandin-like substances isomeric to the COX-derived prostaglandins that are termed isoprostanes. Prostanoids take part in many physiological and pathophysiological processes in practically every organ, tissue and cell, including the vascular, renal, gastrointestinal and reproductive systems. Their activities are mediated through prostanoid-specific receptors and intracellular signalling pathways, whilst their biosynthesis and action are blocked by nonsteroidal antiinflammatory drugs (NSAID). Isoprostanes are considered to be reliable markers of oxidant stress status and have been linked to inflammation, ischaemia-reperfusion, diabetes, cardiovascular disease, reproductive disorders and diabetes. (PMID: 16986207)Prostaglandins are eicosanoids. The eicosanoids consist of the prostaglandins (PGs), thromboxanes (TXs), leukotrienes (LTs), and lipoxins (LXs). The PGs and TXs are collectively identified as prostanoids. Prostaglandins were originally shown to be synthesized in the prostate gland, thromboxanes from platelets (thrombocytes), and leukotrienes from leukocytes, hence the derivation of their names. All mammalian cells except erythrocytes synthesize eicosanoids. These molecules are extremely potent, able to cause profound physiological effects at very dilute concentrations. All eicosanoids function locally at the site of synthesis, through receptor-mediated G-protein linked signalling pathways.