Dependence of serum erythropoietin level on erythropoiesis in leukemia. 
The dependence of the serum erythropoietin (Epo) level on the blood hemoglobin concentration was compared in patients suffering from leukemia and ulcerative colitis.  In leukemia, the level of immunoreactive and bioactive Epo was generally much higher than in ulcerative colitis at comparable degrees of anemia.  The highest Epo values were found in patients with severe bone marrow insufficiency of erythropoiesis.  These findings support the hypothesis that the plasma level of Epo depends not only on the hemoglobin concentration of the blood but is also influenced by the proliferative activity of the erythron.