Figure 1.

Distribution of iron in the adult human body and regulation of iron traffic. Circulating iron is bound to transferrin (holo-Tf) and delivered to tissues (black arrows). Holo-Tf is primarily replenished by iron recycled from tissue macrophages (thick red arrow), but also by dietary iron absorbed by duodenal enterocytes (thin red arrow). Under conditions of iron deficiency, iron stored in hepatocytes can also be mobilized (thin red arrow). Iron efflux to the bloodstream is inhibited by the liver-derived peptide hormone hepcidin, which binds to the iron exporter ferroportin (FPN) and promotes its degradation.