Serum erythropoietin concentration in chronic renal failure: relationship to degree of anemia and excretory renal function

By use of the fetal mouse liver cell assay, serum erythropoietin (SEp) concentration was measured in 135 patients at various stages of chronic renal failure and in 59 healthy subjects. In patients with creatinine clearances (CCr) ranging from 2 to 40 ml/min/1.73 sq m, endocrine renal function was found to deteriorate in parallel to excretory renal function. The known negative correlation between SEp and hematocrit (Hct) was not apparent, probably because of the loss of renal mass accompanying progress of anemia and renal insufficiency. In contrast, in patients with minimal variation of residual excretory renal function, as in individual patients investigated repeatedly within a short period of time, changes of Hct were always accompanied by opposite changes of corresponding SEp concentrations. Thus, patients with chronic renal failure have a sustained regulatory feedback mechanism between Hct and SEp, which probably works at a lower level.