Serum erythropoietin level: relationships to blood hemoglobin concentration and erythrocytic activity of the bone marrow.

The question as to whether the serum concentration of erythropoietin is relatively high for the degree of anemia in patients with erythrocytic hypoplasia has regained interest, since recombinant human-like erythropoietin has become available as a drug for replacement therapy. We have compared the concentration of serum immunoreactive erythropoietin in nonrenal anemic patients with erythrocytic hypoplasia (22 cases) or active erythropoiesis (82 cases). In both groups a negative correlation was determined between the blood hemoglobin concentration and the logarithm of the erythropoietin concentration. However, the two regression lines were not identical, and the serum erythropoietin concentration was significantly higher for the degree of anemia in the patients with erythrocytic hypoplasia. Additional measurements in four patients suffering from acute leukemia with marrow failure showed that the erythropoietin concentration decreased towards the values observed in anemic patients with active erythropoiesis when the erythron recovered in the early phase of complete remission. These data support the idea that, independent of the O2 offer, the proliferating erythrocytic progenitors by negative feedback lower the blood level of erythropoietin.