Glutathione Peroxidase is a family of enzymes that function to reduce peroxides, such as lipid peroxides and hydrogen peroxide, to less damaging components and protect cells from oxidative damage. The mechanism behind this involves, in essence, the reaction of reduced gluthatione with hydrogen peroxide to produce oxidized glutathione and water. Eight isoforms of this enzyme has been identified in humans: GPX1 (glutathione peroxidase 1), GPX2 (glutathione peroxidase 2, gastrointestinal), GPX3 (glutathione peroxidase 3, plasma), GPX 4 (glutathione peroxidase 4, phosopholipid hydroperoxidase), GPX5 (glutathione persoxidase 5, epididymal secretory), GPX6 (glutathione peroxidase 6, olfactory), GPX7 (glutathione peroxidase 7), GPX8 (glutathione peroxidase 8, putative).