Iron Kinetics and Laboratory Assessment

Question 1

What are the percentages of iron

utilization in the body ?

Answer 1

• 70% is in hemoglobin and red blood cells at various stages of development
• 20% is in storage
  
  • mostly within hepatocytes and macrophages in the spleen and bone marrow
• 10% is divided amongst muscle and other enzymes and plasma

Question 2

What is the main way iron in the body is controlled ?

Answer 2

• only can control absorption
• there is no way to really get rid of iron in the body
  
  • with the exception of menstruation

Question 3

What is the protein that transports

iron across luminal membranes, particularly in enterocytes

where it is absorbed ?

Answer 3

• Ferroportin
  
  • transports reduced iron only (ferrous 2+ iron)

Question 4

What is the main regulator

of Ferroportin ?

Answer 4

• Hepcidin
  
  • produced by liver hepatocytes which sense levels of iron in the body
  • hepcidin binds to ferroportin and inactivates it
    
    • high iron in body, increased hepcidin, decreased iron absorption by ferroportin

Question 5

What is the main molecule that transports

iron in the plasma ?

Answer 5

• Transferrin
  
  • iron must first be re-oxidized to ferrous form for transport as it leaves the enterocyte

Question 6

What is the main storage protein for iron ?

Answer 6

• Ferritin
  
  • generally a cytoplasmic protein but also found within mitochondria
  • can bind more than 4000 iron ions
  • partially degraded ferritin is known as hemosiderin and is less metabolically active

Question 7

What are serum iron levels and total

iron binding capacity measures of ?

Answer 7

• serum iron levels:
  
  • indicator of avaialable iron for transport
• total iron binding capacity:
  
  • indirect indicator of transferrin levels