Figure 1.

Model of the systemic regulation of iron exchange. Ferroportin (FPN) is the only known cellular iron exporter in vertebrates and it is mainly expressed by enterocytes and macrophages (exemplified by the cells shown here). Increased erythropoiesis and hypoxia suppress hepcidin production by the liver, and iron absorption or iron release proceed unopposed (cell on the left). Increased iron stores and inflammation induce hepcidin production by the liver; this causes the internalization and degradation of ferroportin by target cells, thus blocking enterocyte iron absorption and iron recycling by macrophages (cell on the right).