Model of regulation of erythropoiesis and hepcidin by Tfr2. Regulation of erythropoiesis and hepcidin in WT mice in normal iron status (upper left panel) and in ID (upper right panel). Regulation of erythropoiesis and hepcidin in the absence of Tfr2 in normal conditions (lower left panel) and in ID (lower right panel). Arrow thickness indicates activity or binding. Bold character indicates increase concentration. Dotted lines indicate lack of binding. Dotted Tfr2 represents membrane destabilization from a lack of the ligand (2Fe-Tf). Tf, apotransferrin; 2Fe-Tf, diferric transferrin.