Understanding Iron Metabolism and Anemia

Nov 26, 2024

Iron Metabolism and Deficiency Anemia

Importance of Iron

  • Essential for metabolic processes:
    • Oxygen transport
    • DNA synthesis
    • Electron transport
  • Iron deficiency:
    • Decreased total body iron content
    • Leads to iron deficiency anemia when red blood cell production is diminished

Iron Metabolism

  • Average 70 kg person:
    • Total body iron content: ~4 grams
    • Hemoglobin: ~2500 mg
    • Circulating in plasma: ~4 mg
    • Stored as ferritin: ~1000 mg
    • Myoglobin and enzymes: ~300 mg
  • Daily iron cycle:
    • Intestinal absorption: 1-2 mg
    • Loss from body: 1-2 mg
    • Red blood cell production: ~20 mg (replenished from recycled iron)

Iron Absorption

  • Dietary Iron Forms:
    • Heme Iron: from animal food, better absorbed
    • Non-Heme Iron: from plant food, poorly absorbed, mostly ferric ion
  • Absorption Process:
    1. Heme iron enters cell
    2. Iron converted to ferric by heme oxidase
    3. Non-heme iron converted to ferrous by duodenal cytochrome B
    4. Ferrous absorbed via DMT1
    5. Ferrous leaves cell via ferroportin
    6. Converted to ferric by hephastin
    7. Binds to transferrin in plasma
  • Excess stored as ferritin
  • Hepcidin: regulates iron metabolism by inhibiting ferroportin

Causes of Iron Deficiency Anemia

  • Dietary Factors:
    • Heme iron well absorbed; non-heme iron absorption impaired by dietary constituents
    • Less meat intake can lead to deficiency
  • Hemorrhage:
    • Blood loss depletes iron stores
    • Chronic bleeding from pregnancy, tumors, NSAIDs, etc.
  • Malabsorption:
    • Conditions like echlorhydria, celiac disease, gastric surgery
  • Rare Causes:
    • Iron refractory iron deficiency (genetic)
    • Hemoglobinuria (conditions affecting kidneys)
    • Pulmonary hemocytosis (intraalveolar bleeding)

Clinical Presentation

  • Gradual development, often asymptomatic at first
  • Symptoms: fatigue, pagophagia, leg cramps
  • Physical signs: pallor, koilonychia, angular stomatitis
  • Complications: hypoxemia, gastric atrophy, impaired immunity

Diagnosis

  • Laboratory Tests:
    • Complete blood count (microcytic hypochromic anemia)
    • Peripheral smear
    • Serum iron, TIBC, ferritin levels
  • Additional tests for etiology: hemoglobinuria, stool testing

Treatment

  • Oral iron therapy
  • Correct underlying causes
  • Avoid iron in conditions like thalassemia
  • Parenteral iron for specific cases, risk of anaphylaxis
  • Androgen replacement in postmenopausal women if needed

Feel free to ask questions or discuss further in the comments section.