Control of marrow production by the level of iron supply.

The level of erythroid marrow production varies widely in different erythropoietic disorders. In part, this reflects the level of erythropoietin stimulation as determined by the severity of the anemia. However, iron supply plays an equally important role in the control of erythropoiesis. As demonstrated in normal individuals subjected to prolonged periods of phlebotomy-induced anemia, the erythroid marrow will increase production by as little as twice to as much as eight times normal, depending on the iron supply available from different iron pools. Whereas the iron delivered from normal reticuloendothelial stores or orally administered iron is sufficient for a marrow production response of only two to three times normal, the increased iron supply from nonviable red cells, hemolysis, or iron dextran infusions permits marrow production to rise acutely to levels of four to eight times normal.