Iron/Heme Metabolism - Goueli Flashcards

1
Q

When prescribing Isoniazid to a patient, what should you be cautious of?

A
  • Vitamin B6 deficiency
    • results i peripheral neuropathy
    • CNS effects
    • anemia (microcytic, hypochromic)
  • Supplement with Vitamin B6 to prevent this!
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2
Q

Why does Vitamin B6 Deficiency commonly result in anemia?

A
  • Vitamin B6 (pyridoxine) is required in the rate limiting step of heme synthesis
    • pyridoxal phosphate is a necessary cofactor for Delta-ALA synthase
    • slowed heme production without VitB6
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3
Q

Heme is degraded to for what?

A

bilirubin

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4
Q

Bilirubin is conjugated with glucuronic acid in what organ?

A

liver

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5
Q

If levels of indirect unconjugated bilirubin are high, what should you be concerned for?

A

Extravascular or Intravascular Hemolysis in the blood

(takes place before it reaches the liver)

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6
Q

If levels of direct conjugated bilirubin are elevated, what should you be concerned about?

A

Liver, Biliary, or Intestinal obstruction

(blockage in the liver and beyond)

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7
Q

Greater than 50% of patients with sporadic Porphyria Cutanea Tarda (deficiency of hepatic uroporphyrinogen decarboxylase or URO-D) also test positive for what hepatic condition?

A

Hepatitis C (HCV positive)

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8
Q

In a 60 yoa male patient with diagnosed iron deficiency anemia of unknown cause, what should your first move in management/treatment be?

A

Look for GI Bleed with Colonoscopy!

  • find source of blood loss first
    • rule out malignancy:
      • gastrointestinal, genitourinary, colorectal, gastric, endometrial, cervical, bladder
  • then rule out malabsorption
    • celiac disease
    • H-pyloria
  • rule out intravascular hemolysis
  • finally, supplement/fortify diet with iron
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9
Q

What causes Anemia of Chronic Disease (AOCD)?

A
  • Inflammation (IL-6/IL-1) increases hepatic transcription, expression, synthesis of hepcidin
    • increased hepcidin stops iron from leaving cells
      • destroys ferroportin (only known exporter of iron)
    • iron stores increased, but decreaded iron utilization (unavailable)
    • not enough iron available to keep up with demands of erythroid proliferation
    • results in hypoproliferative anemia
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10
Q

What is the difference between Ferritin vs. Transferrin in iron metabolism?

A
  • Ferritin
    • iron storage in cytosol
    • high synthesis in high iron states
  • Transferrin
    • plasma iron transporter
    • delivers iron released by macrophages and enterocytes to bone marrow
    • high synthesis in low iron states
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11
Q

What will iron panel tests show in Iron Deficiency Anemia?

(Serum Iron, Serum Ferritin, Transferrin iron saturation, Total Iron Binding Capacity, Transferrin, Hemoglobin)

A
  • Serum Iron: Low
  • *Serum Ferritin: LOW
  • Transferrin iron saturation %: Low
  • Total Iron Binding Capacity: High
  • Transferrin: High
  • Hemoglobin: LOW
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12
Q

What will iron panel tests show in Anemia of Chronic Disease?

(Serum Iron, Serum Ferritin, Transferrin iron saturation, Total Iron Binding Capacity, Transferrin, Hemoglobin)

A
  • Serum Iron: Low
  • Serum Ferritin: High
  • *Transferrin iron saturation %: LOW
  • Total Iron Binding Capacity: Low
  • Transferrin: Low
  • Hemoglobin: Low
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13
Q

What will iron panel tests show in Hemachromatosis?

(Serum Iron, Serum Ferritin, Transferrin iron saturation, Total Iron Binding Capacity, Transferrin, Hemoglobin)

A
  • Serum Iron: High
  • Serum Ferritin: High
  • *Transferrin iron saturation %: HIGH (>45%)
  • Total Iron Binding Capacity: Low
  • Transferrin: Low
  • Hemoglobin: Normal
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14
Q

How do HFE gene mutations cause iron overload in Type 1 Hereditary Hemachromatosis?

A
  • HFE = transmembrane protein belonging to MHC Class I, expressed highly in the liver
    • Helps regulate hepcidin expression (w/ TfR1/TfR2)
  • HFE Mutation: usually cysteine → tyrosine substitution at amino acid 282 (C282Y)
    • results in lack of interaction of HFE w/ TfR2 and reduced cell surface expression
      • decreased hepcidin expression (no regulator of iron absorption)
      • increased Fe absorption
      • decreased storage of iron in macrophages
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15
Q

What are the two forms of dietary iron?

A
  • Heme iron
    • hemoglobin and myoglobin in beef, chicken, fish, etc.
  • Non-heme iron (Fe3+)
    • cereal, vegetables, fortified flour
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16
Q

Which form of dietary iron is best absorbed? Why?

A
  • Heme iron best absorbed
    • hemoglobin/myoglobin in beef, chicken, fish, etc.
  • Iron absorption is enhanced by gastric acid in the proximal small bowel (duodenum)
    • Fe2+ valence absorption = better
    • Heme iron is in ferrous form (Fe2+)
    • Non-heme iron is usually present in the ferric form (Fe3+)
    • Heme Fe > Non-Heme Fe