EPO Became the Drug of Choice for Endurance Athletes

Erythropoietin, or EPO, is a hormone naturally produced by the kidneys that stimulates red blood cell production. When synthetic EPO became available as a medical treatment for anemia, endurance athletes quickly realized its potential. By artificially boosting red blood cell counts, EPO dramatically improves oxygen delivery to muscles, giving cyclists, runners, and cross-country skiers a significant advantage. The drug became rampant in professional cycling during the 1990s, with estimates suggesting up to 90% of riders were using it. However, the health risks are severe. EPO can thicken the blood so much that it causes heart attacks or strokes, especially during sleep when heart rate drops. At least 18 European cyclists died suddenly in the late 1980s and early 1990s, many believed to be EPO-related.