Erythropoietin-- measurement and clinical applications.

Erythropoietin (EPO) is an endogenous hormone produced primarily by the kidney which controls the production of erythrocytes. The main stimulus to production is low tissue oxygen (hypoxia) and EPO triggers the formation of red blood cells by binding to a receptor on erythroid progenitor target cells. Alteration in the EPO regulatory system produces a change in circulating EPO in a variety of disease states, such as renal anaemia and polycythaemia. The availability of recombinant EPO in the 1980s transformed the treatment of anaemia, particularly anaemia of end stage renal disease, and led to the development of more sensitive and specific assays for the measurement of EPO. There are more widespread uses for EPO and preliminary studies indicate that EPO may be useful as a neuroprotective agent by reducing inflammation near the site of injury. The use of EPO to boost endurance in athletes has attracted unwanted publicity, although analytical techniques are now available that can differentiate between endogenous and recombinant EPO. Different types of erythropoietic agents have been developed with a longer plasma half-life and the ability to maintain haemoglobin levels for longer periods and reduce the need for frequent dosing with EPO.