RE: Erythropoietin (EPO)
Erythropoietin is produced in the kidney and stimulates the production of red blood cells. You may have heard of cyclists especially using 'EPO'. EPO's effect is to raise hematocrit levels allowing the blood to carry more oxygen. It is documented that the endurance process is improved in athletes with an increased red blood cell level, and thus an increased oxygen carrying capacity.
Although no direct links have been made between EPO and cycling deaths, anecdotal evidence is abundant. Too much r-EPO can increase hematocrit to the point that overall blood viscosity is increased making the blood like sludge. This thickened blood could cause the heart to work excessively hard, which may lead to a heart attack. Increasing hematocrit also increases the risk in the cyclist for clotting events, raises blood pressure, and resultant iron overload can ultimately lead to organ failure.