The erythropoietin-hematocrit relationship in normal and polycythemic man: implications of marrow regulation.

(juirements.’ Changes in need are met in part by changes in the circulating red cell mass. Accordingly, erythropoietin has been demonstrated in the urine and plasma of patients with anemia or polycythemia of varying origin. However, investigations relating erythropoietin to erythropoiesis in normal mdividuals have only recently been made possible by improved assay methods. This study was undertaken to clarify the normal erythropoietin response to phlebotomy and to better define the relationship of erythropoietin to erythroP0ieSi5 in various polycythemic states.