Prostaglandin F2b is a naturally occurring isoprostane. Isoprostanes are arachidonic acid metabolites produced by peroxidative attack of membrane lipids. These accumulate to substantial levels in many clinical conditions characterized in part by accumulation of free radicals and reactive oxygen species, including asthma, hypertension and ischemia-reperfusion injury. For this reason, they are frequently used as markers of oxidative stress; however, many are now finding that these molecules are not inert, but in fact evoke powerful biological responses in an increasing array of cell types. In many cases, these biological effects can account in part for the various features and manifestations of those clinical conditions. Thus, it may be possible that the isoprostanes are playing somewhat of a causal role in those disease states. Lipid-peroxidation forms primary- or secondary-end products like conjugated dienes, lipid hydroperoxides, gaseous alkanes, and prostaglandin F2-like products. They are created as major products by free-radical catalyzed peroxidation of esterified arachidonic acid (AA) in membrane phospholipids. They are also minor products of the activity of platelet cyclooxygenase-1 (COX-1) in response to stimuli such as collagen, thrombin, or arachidonate. The levels of Prostaglandin F2b and F2-isoprostanes in CSF and urine are elevated in Alzheimer's disease (AD) patients when compared to that of age-matched controls. (PMID: 15275956, 14504139)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.