Erythropoietin is commonly referred to as EPO. It is also called haematopoietin or haemopoietin, but these names are rarely used today.
Erythropoietin is a hormone that is produced predominantly by specialised cells in the kidney. Once it is made, it acts on red blood cells to protect them against destruction. At the same time it stimulates stem cells of the bone marrow to increase the production of red blood cells.
Althought the precise mechanisms that control the production of erythropoietin are poorly understood, it is well known that specialised cells in the kidney are capable of detecting and responding to low levels of oxygen through increased production of erythropoietin. When there is sufficient oxygen in the blood circulation, the production of erythropoietin is reduced, but when oxygen levels go down, the production of erythropoietin goes up. This is adaptive because it facilitates the production of more red blood cells to transport more oxygen around the body, thus raising oxygen levels in the tissues. For example, erythropoietin production will go up when moving to a high altitude. This is because the air pressure is lower, the pressure of oxygen is lower and so less oxygen is taken up by the blood therefore stimulating erythropoietin production. In low oxygen states people risk developing hypoxia - oxygen deprivation. Hypoxia can also occur when there is poor ventilation of the lungs such as occurs in emphysema and in cardiovascular disease. The production of erythropoietin decreases in kidney failure and various chronic diseases such as AIDS, certain cancers and chronic inflammatory diseases like rheumatoid arthritis.
Excess erythropoietin results from chronic low oxygen levels or from rare tumours that produce high levels of erythropoietin. It causes a condition known as polycythaemia which is a high red blood cell count. In many people, polycythaemia does not cause any symptoms. However, there are some general and non-specific symptoms including weakness, fatigue, headache, itching, joint pain and dizziness.
If you have too little erythropoietin, which is usually caused by chronic kidney disease, there will be fewer red blood cells and you will have anaemia. Erythropoietin has been made synthetically for the treatment of anaemia that results from chronic kidney failure. It is also given to patients with some rarer types of cancer.
Some professional athletes have used this type of erythropoietin (known as blood doping) to improve their performance, particularly to increase endurance. Artificially increasing your erythropoietin levels produces more haemoglobin and red blood cells and therefore improves the amount of oxygen that can be delivered to tissues, particularly muscles. This can improve performance, although this type of doping practice is banned by most professional sport committees.
Last reviewed: Dec 2016