Omeostasi della crasi ematica ed eritropoietina

The human erythron includes the erythroid bone marrow, where red cells are produced, and circulating red cells. Red cell production is a very dynamic process, regulated by several factors. The most important factor is erythropoietin, which behaves as a true hormone. In fact, erythropoietin is primarily made by a single organ, the kidney, outside the bone marrow and participates in a classic negative feedback control system. Hypoxia is the fundamental physiologic stimulus that increases renal production. Erythropoietin is mainly a survival factor for human erythroid progenitors cells and expands erythropoiesis by acting at this early stage. Serum erythropoietin levels in normal individuals are in the range of 5 to 15 mU/mL. However, levels found in anemic patients cannot be simply compared with normal values but must be evaluated in relation to the degree of anemia, in order to account for the hypoxic stimulus.