Model effect of erythropoiesis on hepcidin expression between RBC's transfusions. Ultimate hepcidin concentrations are the sum of effects from multiple regulators. RBC transfusions both suppress endogenous erythropoiesis and ultimately result in the accumulation of iron, released from transfused RBCs at the end of their life cycle. Thus, hepcidin is initially derepressed after RBC transfusion and progressively decreases to pretransfusion levels, mirroring hemoglobin and endogenous erythropoietin concentrations (modified from data in Ghoti et al¹⁵ ). epo, erythropoietin; Hb, hemoglobin; TX, transfusion.