THE ENDOGENOUS ERYTHROPOIETIN RESPONSE AND THE ERYTHROPOIETIC RESPONSE TO BLOOD-LOSS ANEMIA - THE EFFECTS OF AGE AND GENDER

The endogenous erythropoietin (EPO) response and the erythropoietic response to anemia in the elderly, as compared with that in younger subjects, is controversial. We therefore studied autologous blood donors undergoing aggressive phlebotomy to determine the effect of age and gender on the EPO response to blood loss anemia, along with the erythropoietic response to endogenous EPO and to exogenous recombinant human EPO therapy. Seventy-one patients underwent phlebotomy, up to 6 units over 3 weeks, and received either placebo (n = 18), EPO 150 U/kg (n = 16), EPO 300 U/kg (n = 18), or EPO 600 U/kg (n = 19) at each of the six visits. Linear regression analysis of the hemoglobin/log EPO relationship for 18 placebo patients revealed no differences in the endogenous EPO response to phlebotomy, as determined by the slopes and intercepts, for males versus females or as a function of age. We found no differences in endogenous EPO-stimulated red blood cell (RBC) volume expansion for males and females (7.06 +/- 2.4 and 7.22 +/- 2.2 ml/kg, respectively, p = 0.88) or as a function of age (estimated rate of change = -0.58 +/- 0.33 ml/kg for every 10 years of life, p = 0.10). Similarly, we found no differences in RBC response to EPO for males versus females (1.4 +/- 0.3 ml/kg vs 1.5 +/- 0.3 ml/kg per 1000 U/kg EPO, respectively, p = 0.80) or as a function of age (estimated rate of change = 0.051 +/- 0.15 ml/kg per 1000 U/kg EPO for every 10 years of life, p = 0.74). In conclusion, we could detect no differences in the endogenous EPO response to blood loss anemia nor in the erythropoietic response to either endogenous or exogenous EPO when we analyzed for patient gender and age.