Category: transport
Iron absorption: dietary Fe3+ reduced to Fe2+ at the duodenal brush border (DCYTB) → imported by DMT1 → exported to plasma by ferroportin (FPN). Plasma iron binds transferrin → delivered to erythroblasts (transferrin-R) + stored in ferritin in liver / macrophages / enterocytes. HEPCIDIN (hepatic peptide hormone) is the master regulator: high hepcidin internalizes + degrades ferroportin → blocks export from enterocytes + macrophages → plasma iron falls. Hepcidin is upregulated by iron load + inflammation (IL-6 — explains anemia of chronic inflammation), downregulated by erythropoietic drive (erythroferrone from erythroblasts). Hereditary hemochromatosis = HFE mutations → low hepcidin → unrestricted absorption.