Erythropoietin, otherwise known as EPO, is an endocrine hormone produced by specialized renal cells, and acts on the stem cells in the bone marrow to increase the production of red blood cells in the process known as erythropoiesis. The levels of EPO in the blood is dependant upon oxygen concentration in the blood, when the oxygen concentration is low EPO production increase, when the concentration is high, EPO production drops.,
There is a synthetic substitute for EPO, known as recombinant Human EPO or rHuEpo which is designed to aid in the treatment of severe anaemia in patients who have suffered renal failure and are therefore unable to create the hormone themselves. It is also used in cases where the patients with neoplasms, myelodysplastic syndromes, HIV infection, rheumatoid arthritis, and aplastic anemia.
EPO has also caused much furore within the world of professional athletics, due to its ability to dramatically increase the oxygen carrying capabilities of the users blood and therefore the users stamina, coupled with the fact that it is a naturally occurring substance within the body, and therefore very hard to test for. These factors led to the drugs increased use within many sports, most notably within cycling, when the 1998 Tour De France was badly disrupted, and one team, Festina, were thrown out, causing five others to retire in support when EPO was found in the team support vans. There were concerns as to how legitimate any records made at the Sydney 2000 Olympics were due to the unknown number of athletes taking the drug, but a short time before the Games, Sydney officials announced they had a combined blood/urine test that could pick up excess EPO in the blood, and in doing so, hopefully deterred many would-be cheats.