[Decrease serum erythropoietin level induced by iron replacement therapy in patients with iron deficiency anemia]

The relationship between serum erythropoietin (EP) and hemoglobin (Hb) concentrations was investigated in patients of iron deficiency anemia (IDA) in the course of iron replacement therapy to elucidate how the therapy induced changes in that relationship. At first Hb-dependent EP levels were determined in 123 IDA patients prior to the treatment by the third-degree logarithmic regression of EP on the Hb deficit (d-Hb). Following the start of iron supply, the deviation of observed EP values from the predicted level (EPc), i.e., delta-EP, was most obvious at the next phase of the onset of reticulocyte crisis; however, this deviation reduced with the alleviation of IDA. The value in maximum phase (delta-EPmx), as individually defined for each of 95 patients, correlated significantly with the severity of the pretreatment ID state (r = 0.502, p < 0.01). Partial correlation analysis revealed that about 80% of this gap was attributable to the ID state. Also, it was assumed that EP upregulation was twice that attributable to the Hb-deficit factor alone. The phase sequence of the delta-EP versus d-Hb relationship in 21 relapsed patients demonstrated a different rout from that observed in their improvement phase. The ID state-induced upregulation of EP, i.e., EPc, was followed by a therapy-induced overshooting drop that was attributable to acute uptake of EP by shifted erythroid precursors. From the viewpoint of erythropoietic regulation, the subsequent down-regulation of EP in the mid to late phases was considered appropriate for the prevention of Hb over production.