Iron is loaded onto diferric transferrin from three sources: the gut (diet), macrophages (recycled iron), and the liver (stored ferritin iron). Iron deficiency anemia is typically associated with low iron saturation of available transferrin. The most immediate source of iron for erythroblasts is mono- or diferric transferrin, found in high concentrations in the plasma.
Iron is central to hemoglobin structure and function ( Perutz 1982). (From Andrews 2008 reprinted, with permission, © American Society of Hematology.)Įrythrocytes and their precursors require large amounts of iron for the production of heme ( Fig. This recycling pathway is supported by ( A) intestinal iron absorption, ( B) erythrophagocytosis, ( C) hepatic iron stores, and ( D) iron incorporation into hemoglobin.
Each day, 20 mg of iron is recycled between circulating transferrin (Fe-Tf) and erythrocytes. In the event of hemorrhage, additional iron must be absorbed from the diet to meet the steady-state demands of the host. Owing to a shorter half-life of circulating erythrocytes in iron deficiency anemia, iron is recovered sooner in those patients, but the amount of iron in each microcytic erythrocyte is reduced ( Macdougall et al. Approximately 20 mL of senescent erythrocytes are cleared daily, and the 20 mg of iron in those cells is recycled for the production of new erythrocytes. Tissue oxygenation requirements and erythrocyte production generally remain stable during adulthood in the absence of hemorrhage, disease, or altered physical activity. Erythropoiesis-related demands for iron are created by three variables: tissue oxygenation, erythrocyte turnover, and erythrocyte loss from hemorrhage. To more fully understand iron deficiency anemia, consideration must be directed toward concepts of iron supply and demand for the production of erythrocytes. Based on the location of hemoglobin in erythrocytes, anemia is a characteristic trait of iron deficiency.ĭespite iron’s plentifulness on earth, iron deficiency is extremely common in humans, and is the most prevalent cause of anemia worldwide. More than one-half of total-body iron is contained within hemoglobin. Hemoglobin is the most abundant iron-containing protein in humans. Among these four categories, the first three protein groups are detected at lower levels, but they are functionally important. įour general categories of proteins contain iron: (1) mononuclear iron proteins (e.g., superoxide dismutase), (2) diiron-carboxylate proteins (e.g., ribonucleotide reductase, ferritin), (3) iron-sulfur proteins (e.g., aconitase), and (4) heme proteins (e.g., hemoglobin). An excellent source of information is provided at. Growing lists of biomolecules that bind or incorporate iron are being catalogued according to their structural similarities. Its redox states make iron useful for evolving biological processes.
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