Iron Kinetics and Lab Assessement

• What percentage of body iron is found in hemoglobin?

  70%
• Where is 20% of body iron stored?

  In hepatocytes and macrophages
• What percentage of body iron is divided among muscles and enzymes?

  10%
• What are the three compartments of body iron distribution?

  • Functional compartment: Iron in hemoglobin, myoglobin, cytochromes
  • Storage compartment: Non-functioning iron in macrophages and hepatocytes
  • Transport compartment: Iron in transit between body sites
• What is the primary source of recycled iron in the body?

  Red blood cells
• How do macrophages contribute to iron recycling?

  They ingest senescent red blood cells
• What protein enables macrophages to export iron?

  Ferroportin
• What does exported iron bind to?

  Apotransferrin
• What is the role of haptoglobin in iron transport?

  It binds to hemoglobin
• What does hemopexin bind to?

  It binds to heme
• Why can't haptoglobin and hemopexin pass through the glomerulus?

  They are proteins
• What foods are high in iron?

  Red meats, legumes, dark leafy vegetables
• In what forms can iron be absorbed?

  As ionic or nonionic iron
• How much iron is typically absorbed in the US diet?

  1 to 2 mg
• Who typically needs additional iron supplementation?

  Menstruating women, pregnant women, children
• What are the laboratory tests for assessing body iron status?

  • Serum Iron: Indicator of available transport iron
  • Total Iron-Binding Capacity: Indirect indicator of transferrin level
  • Percent Transferrin Saturation: Indicator of transport iron
  • Prussian Blue Staining: Visual assessment of tissue iron stores
  • Zinc Protoporphyrin: Indicator of functional iron in red blood cells
  • Ferritin: Indicator of iron stores
  • Soluble transferrin receptor: Indicator of functional iron in cells
  • Hemoglobin Content of Reticulocytes: Indicator of functional iron in developing RBCs
• What does serum iron indicate?

  Available transport iron
• When should serum iron be collected for testing?

  Fasting specimen early in the morning
• What does Total Iron-Binding Capacity indicate?

  Transferrin level
• How is Percent Transferrin Saturation calculated?

  Serum Iron / TIBC x 100%
• What is Prussian Blue Staining used for?

  Assessment of body iron stores
• What does Zinc Protoporphyrin indicate?

  Functional iron available in red blood cells
• When does Zinc Protoporphyrin accumulate in red blood cells?

  When iron is not incorporated into heme
• What does ferritin indicate?

  Iron stores
• What can falsely increase ferritin levels?

  Infection or inflammation
• What does the soluble transferrin receptor indicate?

  Functional iron available in cells
• What happens to hemoglobin content of reticulocytes when iron is restricted?

  It drops
• What is the significance of the Thomas Plot in iron studies?

  It is used to assess iron status and metabolism.