 Surprisingly, knockout of GPX4 heterozygously in mice (GPX4+/−) increases their median life span.Knockout studies with GPx1, GPx2, or GPx3 deficient mice showed that cytosolic GPx4 is so far the only glutathione peroxidase that is indispensable for embryonic development and cell survival.As mechanisms to dispose of both hydrogen peroxide and lipid hydroperoxides are essential to life, this indicates that in contrast to the multiple metabolic pathways that can be utilised to dispose of hydrogen peroxide, pathways for the disposal of lipid hydroperoxides are limited.