Erythropoietin

Erythropoietin is a glycoprotein produced principally by fibroblast-like cells in the renal interstitium and is the major stimulus for erythropoiesis.

Loss of renal substance, with decreased erythropoietin production, results in a normochromic, normocytic anaemia. Conversely, erythropoietin secretion may be increased, with resultant polycythaemia, in patients with polycystic renal disease, benign renal cysts or renal cell carcinoma.

Recombinant human erythropoietin has been biosynthesized and is available for clinical use, particularly in patients with renal failure. Severe kidney dysfunction causes reduction in the plasma levels of erythropoietin, resulting in chronic anaemia - injection of purified erythropoietin into the blood stream can help to relieve this type of anaemia.

Erythropoietin is given by subcutaneous injection initially three times a week in conjunction with an oral iron supplement. The red cell count is measured weekly at first and the dose is modified accordingly.

Levels of erythropoietin in plasma fluctuate with varying oxygen tension of the blood, but androgens and prostaglandins also modulate the levels to some extent.

The most common method of monitoring is via a test called a “packed cell volume” or “hematocrit” as these tests are readily run in the hospital without sending samples to an outside laboratory. This test may be used to help determine the cause of anemia, polycythemia (high red blood cells) or other bone marrow disorders. These cells are sensitive to the oxygen concentration in the blood, and increase the release of EPO when the oxygen concentration is low. Since oxygen is carried by red blood cells, too few red blood cells (anemia) will result in erythropoietin release.

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