What is ERYTHROPOIETIN?

Also Known As: EPO

Erythropoietin (EPO) is a hormone produced primarily by the kidneys, with small amounts made by the liver. EPO plays a key role in the production of red blood cells (RBCs), which carry oxygen from the lungs to the rest of the body. This test measures the amount of erythropoietin in the blood.

The body uses a dynamic feedback system to help maintain sufficient oxygen levels and a relatively stable number of RBCs in the blood.

• Erythropoietin is produced and released into the blood by the kidneys in response to low blood oxygen levels (hypoxemia). The amount of erythropoietin released depends on how low the oxygen level is and the ability of the kidneys to produce erythropoietin.
• EPO is carried to the bone marrow, where it stimulates the production of red blood cells. The hormone is active for a short period of time and then eliminated from the body in the urine.
• As oxygen levels in the blood rise to normal or near-normal levels, the kidneys slow the production of EPO.

However, if your kidneys are damaged and do not produce enough erythropoietin, then too few RBCs are produced and you can become anemic. Similarly, if your bone marrow is unable to respond to the stimulation from EPO, then you may become anemic. This can occur with some bone marrow disorders or with chronic diseases, such as rheumatoid arthritis. (Read Anemia of Chronic Diseases to learn more.)

If you have a condition that affects the amount of oxygen you breathe in, such as lung disease, you may produce more EPO to try to compensate for the low oxygen level. People who live at high altitudes may also have higher levels of EPO and so do chronic tobacco smokers.

If you produce too much erythropoietin, which can happen with some benign or malignant kidney tumors and with a variety of other cancers, you may produce too many RBCs (polycythemia or erythrocytosis). This can lead to an increase in the blood’s thickness (viscosity) and sometimes to high blood pressure (hypertension), blood clots (thrombosis), heart attack, or stroke. Rarely, polycythemia is caused by a bone marrow disorder called polycythemia vera, not by increased erythropoietin.