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Erythropoietin

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Erythropoietin is a hormone produced mainly in the kidneys which stimulates the production and maintenance of red blood cells.
Erythropoeitin testing in sport.

Erythropoeitin testing in sport. Blood sample being tested for the presence of the performance-enhancing hormone erythropoeitin.

Alternative names for erythropoietin

Erythropoietin is commonly referred to as EPO.  It is also called haematopoietin or haemopoietin, but these names are rarely used today.

What is erythropoietin?

Erythropoietin is a hormone which 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 theproduction of red blood cells. 

How is erythropoietin controlled?  

The mechanisms that control the production of erythropoietin are poorly understood.  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.

What happens if I have too much erythropoietin?

Excess erythropoietinresults 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.  

What happens if I have too little erythropoietin?

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 erythropoietinlevels 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.

 

Written: July 2012

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