Test Information

Erythropoietin (EPO) is a glycoprotein hormone primarily produced by kidneys and regulates red cell production by bone marrow (erythropoiesis). In healthy persons there is inverse correlation between serum EPO and hematocrit; an exponential increase in EPO occurs as hematocrit decreases. Under conditions of hypoxia, the level of EPO in the circulation increases, leading to increased production of red blood cells. EPO levels in anemia are determined by the degree of anemia and not by specific effect of underlying illness on the production of EPO.
Presence of EPO level in the blood can indicate bone marrow disorders, (such as polycythemia or increased red blood cell production), kidney disease or erythropoietin abuse (Erythropoietin has been misused as a performance-enhancing drug by some athletes). Primary polycythemia (polycythemia vera) is a neoplastic (clonal) blood disorder characterized by autonomous production of hematopoietic cells. Increased erythrocytes result in compensatory suppression of EPO levels.
Various types of secondary polycythemias are associated with the production of elevated levels of EPO. Secondary polycythemias (e.g., high-altitude living and pulmonary disease) are characterized by hypoxia and a compensatory increase in red cell mass. EPO production is increased in an attempt to increase the delivery of oxygen by increasing the number of oxygen-carrying RBCs. In other instances, elevated EPO levels are the result of production by neoplastic cells. Some tumors secrete EPO or EPO-like proteins; examples include tumors of the kidney, liver, lung, and brain.
Abnormal EPO levels also may be seen in renal failure. Chronic renal failure may result in decreased renal EPO production and, subsequently, anemia.