Human erythropoietin is member of the EPO/TPO family and encodes a secreted, glycosylated cytokine hormone composed of four alpha helical bundles. The protein is found in the plasma and regulates red cell production by promoting erythroid differentiation and initiating hemoglobin synthesis. This protein also has neuroprotective activity against a variety of potential brain injuries and antiapoptotic functions in several tissue types. It is produced by kidney or liver of adult mammals and by liver of fetal or neonatal mammals.