[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Biochemistry](https://durgical.com/en/biochemistry/) › Iron metabolism [Biochemistry](https://durgical.com/en/biochemistry/) · Topic # Iron metabolism The body has no way to excrete iron: it controls how much it absorbs with hepcidin, carries it on transferrin and stores it in ferritin. Updated 2026-11-01 ## Key facts - An adult has 3–4 g of iron; about two thirds is in hemoglobin. - Only 1–2 mg a day is absorbed in the duodenum, the same as is lost; nearly all daily iron (20–25 mg) comes from macrophages recycling old red cells. - Hepcidin (liver) blocks ferroportin, the only exit door for iron from cells: absorption falls and iron is trapped in macrophages. - Ferritin: the store and best marker of reserves (low = deficiency), but it rises with inflammation because it is an acute-phase reactant. ## In detail - Absorption: in the duodenum, duodenal cytochrome b reduces dietary Fe³⁺ to Fe²⁺ and the DMT1 transporter carries it into the enterocyte; heme iron enters by another route and heme oxygenase releases it. - Exit: ferroportin moves it out across the basal side; hephaestin (and ceruloplasmin in plasma) oxidises it to Fe³⁺ so transferrin can take it. - Transport: each transferrin carries two Fe³⁺; it is normally 20–45 % saturated. Cells take it up through transferrin receptor 1 and endocytosis; in the acidic endosome the iron is released. - Storage: ferritin holds up to about 4500 iron atoms in its shell; hemosiderin is degraded ferritin in lysosomes, typical of overload. - Cell control: when iron is low, IRP proteins bind the mRNA IREs: they block translation of ferritin and ALAS2 (5' IRE) and protect transferrin receptor mRNA (3' IRE). - Whole-body control: hepcidin rises with iron excess and inflammation (IL-6); it falls with iron deficiency, hypoxia and active erythropoiesis (erythroferrone). - Vitamin C and heme iron improve absorption; phytates, tannins in tea and coffee, and calcium reduce it. ## Clinical notes - Iron deficiency: low ferritin, high transferrin (TIBC), low saturation; it is the most common cause of anemia worldwide. - Anemia of inflammation: high hepcidin traps iron; normal or high ferritin with low serum iron and low TIBC. - Hereditary hemochromatosis: low hepcidin lets too much iron in; high transferrin saturation (over 45 %) and high ferritin. - Repeated transfusions (thalassemia, sickle cell anemia) cause iron overload because there is no way to excrete it. ## Pathways - [Heme synthesis](https://durgical.com/en/biochemistry/pathways/heme-synthesis/) - [Heme breakdown and bilirubin](https://durgical.com/en/biochemistry/pathways/heme-breakdown-and-bilirubin/) ## Related conditions - [Iron deficiency anaemia](https://durgical.com/en/conditions/iron-deficiency-anaemia/) - [Hereditary hemochromatosis](https://durgical.com/en/conditions/hereditary-hemochromatosis/) - [Thalassemias (α and β)](https://durgical.com/en/conditions/thalassemias/) - [Sickle cell disease](https://durgical.com/en/conditions/sickle-cell-disease/) ## Related - [Heme](https://durgical.com/en/biochemistry/molecules/heme/) - [Hemoglobin and 2,3-BPG](https://durgical.com/en/biochemistry/enzymes/hemoglobin-and-2-3-bpg/) - [Ferrochelatase](https://durgical.com/en/biochemistry/enzymes/ferrochelatase/) - [Heme oxygenase](https://durgical.com/en/biochemistry/enzymes/heme-oxygenase/) - [ALA synthase](https://durgical.com/en/biochemistry/enzymes/ala-synthase/) ## Test yourself Think of the answer, then tap the question to see it. ## Which protein does hepcidin act on, and with what effect? It binds ferroportin and causes its degradation: intestinal absorption and iron release from macrophages fall. ## How do labs distinguish iron deficiency from anemia of inflammation? In deficiency ferritin is low and TIBC high; in inflammation ferritin is normal or high and TIBC low. ## What does IRP do when the cell is short of iron? It binds the IREs: it blocks ferritin synthesis and stabilises transferrin receptor mRNA to take up more iron. ## What is the main daily source of iron for making hemoglobin? Iron recycled from old red cells by macrophages (20–25 mg a day), far more than the diet. [Add to my cards (4)](https://durgical.app/estudiar/?add=/en/biochemistry/topics/iron-metabolism/) Educational information, not medical advice. For any symptom, see a health professional. Sources: [Reactome | Iron uptake and transport](https://reactome.org/PathwayBrowser/#/R-HSA-917937) (Reactome, 2026); [HAMP gene: MedlinePlus Genetics](https://medlineplus.gov/genetics/gene/hamp/) (MedlinePlus, US National Library of Medicine, 2026); [Ferritin blood test: MedlinePlus Medical Encyclopedia](https://medlineplus.gov/ency/article/003490.htm) (MedlinePlus, US National Library of Medicine, 2026); [Total iron binding capacity: MedlinePlus Medical Encyclopedia](https://medlineplus.gov/ency/article/003489.htm) (MedlinePlus, US National Library of Medicine, 2026); [TF: Serotransferrin (human)](https://www.uniprot.org/uniprotkb/P02787/entry) (UniProt, 2026); [Iron: MedlinePlus](https://medlineplus.gov/iron.html) (MedlinePlus, US National Library of Medicine, 2026). [← All of biochemistry](https://durgical.com/en/biochemistry/) ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/biochemistry/topics/iron-metabolism/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/biochemistry/topics/iron-metabolism/