A complex inflammatory interaction due to IL1, IL2, TNFα, and INFy [51], the effects of hepcidin on iron metabolism [52], the altered intestinal absorption of nutrients, which is essential in erythrocyte maturation and production, and altered hormonal/receptor responses [53] are all additional factors which contribute to the impaired response of bone marrow to erythropoietin and thus to the onset of anemia in CKD. Here, EPO is linked to anemia (phenotype).