(i-rith-row-POY-uh-tun) A protein made by the kidneys. Erythropoietin, also called EPO, is created in response to low oxygen levels in the body (anemia). EPO causes the bone marrow bone marrow: The soft, spongy tissue inside most bones. Blood cells are formed in the bone marrow. to make more red blood cells. A shortage of EPO can also cause anemia anemia: (uh-NEE-mee-uh) A condition in which there is a shortage of red blood cells in the bloodstream. This causes a low red blood cell count. Symptoms of anemia are fatigue and tiredness. .
