Iron and blood
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Iron and Blood: A Comprehensive Overview
Iron Metabolism and Regulation
Iron is a vital element for numerous biological processes, primarily due to its role in oxygen transport and storage. Most of the body's iron is bound to hemoglobin within erythrocytes (red blood cells). The recycling of iron from aged red blood cells is managed by macrophages in the spleen, liver, and bone marrow 1. Dietary iron is absorbed in the duodenum by enterocytes through the divalent metal transporter 1 (DMT1) and transported into the bloodstream via ferroportin (FPN). Once in the blood, iron binds to transferrin and is delivered to various cells, including hepatocytes, macrophages, and bone marrow cells, via transferrin receptor 1 (TfR1) 13.
The liver plays a crucial role in iron storage, primarily in the form of ferritin. When iron levels are high, hepatocytes secrete hepcidin, a hormone that binds to FPN, leading to its internalization and degradation, thereby reducing iron release into the blood 13. This regulatory mechanism ensures that iron homeostasis is maintained, preventing both deficiency and overload.
Iron in Blood and Its Functions
Iron in the bloodstream is involved in several key functions: storage, catalysis, ferrification, and hemoglobin production. Hemoglobin, which contains iron, is essential for oxygen transport from the lungs to tissues 2. Iron's catalytic properties also play a role in various enzymatic reactions, although free iron can be toxic due to its ability to generate free radicals 3.
Iron is transported in the blood bound to transferrin, which prevents its toxic effects and facilitates its delivery to cells. The majority of iron in the body is either in erythrocytes or stored in ferritin complexes within cells, particularly in the bone marrow, liver, and spleen 3.
Iron Deficiency and Supplementation
Iron deficiency is a common global health issue, often leading to anemia. In critical care settings, iron supplementation is used to treat anemia, although its efficacy varies. A systematic review found that iron supplementation in ICU patients did not significantly reduce the need for red blood cell transfusions or improve hemoglobin levels in the short term 4. However, intravenous iron has been shown to be effective in treating iron deficiency in blood donors and preoperative patients, improving iron stores and reducing the need for blood transfusions 67910.
Iron Overload and Genetic Disorders
Iron overload, such as in hemochromatosis, can lead to severe health issues. Hemochromatosis is often caused by genetic mutations, such as those in the HFE gene, which disrupts iron regulation and leads to excessive iron absorption and storage 3. The regulation of hepcidin is also affected in these conditions, further complicating iron homeostasis 3.
Conclusion
Iron is indispensable for life, playing critical roles in oxygen transport, storage, and various metabolic processes. The body tightly regulates iron levels through complex mechanisms involving absorption, transport, storage, and recycling. Both iron deficiency and overload pose significant health risks, necessitating careful management through dietary intake, supplementation, and medical interventions. Understanding these processes is crucial for addressing related health conditions effectively.
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Most relevant research papers on this topic
On Iron Metabolism and Its Regulation
Cellular and systemic iron regulation involves key mechanisms and players, with hepcidin playing a key role in controlling iron release from cells into the blood.
Highly CitedIRON IN HUMAN BLOOD
Blood iron participates in storage, catalysis, ferrification, and hemoglobin production, with the circulatory system transporting and distributing iron stored in the body.
Iron supplementation to treat anaemia in adult critical care patients: a systematic review and meta-analysis
Iron supplementation does not reduce red blood cell transfusion requirements in critically ill adults, but well-designed trials are needed to optimize dosing regimens and identify patients most likely to benefit from iron.
Meta-Analysis
Rigorous JournalA Red Carpet for Iron Metabolism
Iron metabolism plays a crucial role in maintaining blood production and erythropoiesis, with recent progress in understanding systemic and cellular mechanisms underlying iron homeostasis regulation and disorders.
Very Rigorous JournalHighly CitedHigh-dose intravenous versus oral iron in blood donors with iron deficiency: The IronWoMan randomized, controlled clinical trial.
A single dose of 1000 mg of intravenous iron effectively counteracts iron deficiency in blood donors, while oral iron is an acceptable alternative.
RCTVery Rigorous JournalThe Important Role for Intravenous Iron in Perioperative Patient Blood Management in Major Abdominal Surgery: A Randomized Controlled Trial.
Preoperative intravenous iron reduces blood transfusion needs, shortens hospital stays, and improves hemoglobin levels 4 weeks after surgery.
RCTHighly CitedEffectiveness of Iron Supplementation With or Without Erythropoiesis-Stimulating Agents on Red Blood Cell Utilization in Patients With Preoperative Anaemia Undergoing Elective Surgery: A Systematic Review and Meta-Analysis.
Preoperative iron supplementation with erythropoiesis-stimulating agents may reduce red blood cell utilization in patients with anaemia undergoing elective surgery.
Meta-AnalysisOral or parenteral iron supplementation to reduce deferral, iron deficiency and/or anaemia in blood donors.
Oral or parenteral iron supplementation significantly reduces deferral due to low haemoglobin levels in blood donors, potentially increasing blood donation rates.
Meta-AnalysisVery Rigorous JournalRole of preoperative intravenous iron therapy to correct anemia before major surgery: a systematic review and meta-analysis
Preoperative intravenous iron supplementation significantly reduces blood transfusions and increases hemoglobin levels before major surgery, but further randomized controlled trials are needed for more definitive conclusions.
Meta-AnalysisVery Rigorous Journal