Questions and Answers
What is the largest percentage of body iron found in?
Hemoglobin in red blood cells
Where is the 20% of body iron stored?
In hepatocytes and macrophages in the spleen and bone marrow
What is the functional compartment of iron kinetics?
Iron functioning within cells, e.g. hemoglobin, myoglobin, and cytochromes
What is the storage compartment of iron kinetics?
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What is the transport compartment of iron kinetics?
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What percentage of body iron is divided among muscles, cytochromes, enzymes, and plasma?
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Where is myoglobin found?
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What is the role of the storage compartment?
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What is the largest source of recycled iron in the body?
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Where do senescent red blood cells get ingested?
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What molecule enables macrophages to export iron?
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What binds to exported iron?
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In what forms can iron be absorbed?
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What type of foods are high in iron?
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Why is iron recycling important?
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What is the purpose of iron regulation in the body?
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What does haptoglobin bind to?
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What is the average amount of iron absorbed from the US diet?
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What does hemopexin bind to?
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Why are haptoglobin and hemopexin unable to pass through the glomerulus?
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What is the purpose of collecting a fasting specimen for serum iron?
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What does serum iron indicate?
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What type of cells mediate the haptoglobin-hemoglobin complex?
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What type of cells mediate the hemopexin-heme complex?
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What is the total iron-binding capacity an indicator of?
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What is calculated as a percentage of serum iron to total iron-binding capacity?
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What is the gold standard for assessing body iron stores?
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What accumulates in red blood cells when iron is not incorporated into heme?
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What is the consequence of impaired ferrochelatase, such as in lead poisoning?
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What is the relationship between serum iron and TIBC in calculating percent transferrin saturation?
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What is the primary function of transferrin?
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What is the purpose of Prussian blue staining?
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What is ferritin an indicator of in the body?
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What is the limitation of using ferritin as an indicator of iron stores?
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What is the soluble transferrin receptor an indicator of?
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How does the level of soluble transferrin receptor relate to the number of TfR1 on the membrane?
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What is the role of ferritin during an infection or inflammation?
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Why is ferritin not a perfect indicator of iron stores?
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What is the relationship between serum ferritin levels and stored iron in the body?
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What is the significance of TfR1 on the membrane in relation to iron availability?
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Study Notes
Iron Distribution
- 70% of body iron is found in hemoglobin in red blood cells
- 20% is stored in hepatocytes and macrophages in the spleen and bone marrow
- 10% is distributed among muscles, cytochromes, and various iron-containing enzymes, and plasma
Iron Compartments
- Functional compartment: iron functioning within cells (e.g., hemoglobin, myoglobin, cytochromes)
- Storage compartment: iron stored in macrophages and hepatocytes
- Transport compartment: iron in transit from one body site to another
Iron Absorption
- Iron can be absorbed as either ionic or nonionic iron
- High levels of iron are found in red meats, legumes, and dark green leafy vegetables
- Bioavailability: 1-2 mg of iron is absorbed in the US diet, adequate for most men, but not for menstruating women, pregnant and lactating women, and growing children
Iron Transport
- Iron is transported in the blood bound to apotransferrin
- Haptoglobin binds to hemoglobin, mediated by macrophages with haptoglobin-hemoglobin receptor
- Hemopexin binds to heme, mediated by hepatocytes with hemopexin-heme receptor and ferroportin
Iron Recycling
- Largest percentage of recycled iron comes from senescent red blood cells
- Macrophages ingest senescent red blood cells and export iron bound to apotransferrin
Laboratory Assessment of Body Iron Status
- Serum Iron: indicator of available transport iron
- Total Iron-Binding Capacity (TIBC): indirect indicator of transferrin level
- Percent Transferrin Saturation: indirect indicator of transport iron and transferrin level
- Prussian Blue Staining: visual qualitative assessment of tissue iron stores
- Zinc Protoporphyrin (ZPP): indicator of functional iron available in red blood cells
- Ferritin: indicator of iron stores
- Soluble Transferrin Receptor (sTfR): indicator of functional iron available in cells
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Description
Learn about the distribution of iron in the body, including its functional, storage, and transport compartments. Understand the percentage of iron found in different parts of the body.
