Production of [[Erythrocytes|erythrocytes]] is regulated by '''erythropoietin''' (EPO) which is produced in the yolk sac, [[Liver - Anatomy & Physiology|liver]] and kidney from embryonic life until early neonatal life. In the adult it is produced only in the kidneys. Erythropoietin is a glycoprotein hormone and is controled by a negative feedback mechanism. Normal levels are low with sufficient amounts to maintain a basal level of new erythrocyte production. If blood oxygen concentration falls, the release of erythropoietin rises. | Production of [[Erythrocytes|erythrocytes]] is regulated by '''erythropoietin''' (EPO) which is produced in the yolk sac, [[Liver - Anatomy & Physiology|liver]] and kidney from embryonic life until early neonatal life. In the adult it is produced only in the kidneys. Erythropoietin is a glycoprotein hormone and is controled by a negative feedback mechanism. Normal levels are low with sufficient amounts to maintain a basal level of new erythrocyte production. If blood oxygen concentration falls, the release of erythropoietin rises. |