Erythropoetin

The production of red blood cells requires the coordinated interaction of two body systems: the bone marrow, which produces red blood cells, and the kidneys, which synthesize the hormone erythropoietin. Reduced oxygen levels in the blood stimulate the synthesis and release of erythropoietin into the blood. Through the circulatory system, erythropoietin reaches the bone marrow, where it activates the reproduction of red blood cells by stimulating the activity of erythroid progenitor cells. In response to the effects of erythropoietin, the progenitor cells mature into complete red blood cells.

Erythropoietin levels in polycythemia: Evaluation of erythropoietin levels in patients with elevated red blood cells helps differentiate between primary and secondary polycythemia. Polycythemia vera or primary polycythemia is a neoplastic change in the bone marrow in which there is an increased production of red blood cells. In the case of primary polycythemia, the serum erythropoietin level is slightly decreased or less than normal.

Secondary polycythemia is characterized by an increase in the number of red blood cells due to stimulation of their formation. In most clinical cases of secondary polycythemia, erythropoietin levels are normal or elevated.

Erythropoietin levels in anemia: In terminal chronic renal failure (CRF), anemia may develop due to decreased erythropoietin synthesis in the kidneys. In this case, recombinant human erythropoietin is sometimes prescribed to restore red blood cell levels. Thus, it can be concluded that measurement of serum EPO levels can help in the detection of anemia in patients with kidney disease. In mild chronic renal failure, measurement of erythropoietin concentrations is useful in assessing the etiology of anemia, with renal disease excluded as a possible cause.

Patients with chronic diseases, such as inflammatory processes (including rheumatoid arthritis) and neoplastic neoplasms, may also develop anemia of chronic disease (ACHD). In this case, the causes of the disorder are iron sequestration in the mononuclear phagocyte system and insufficient bone marrow response to erythropoietin. In anemia of chronic diseases, the level of erythropoietin in serum is increased. In iron deficiency anemia, serum erythropoietin levels are also increased. High levels of EPO reflect the body's attempts to stimulate bone marrow activity; however, lack of iron inhibits red blood cell reproduction.