Flashcards in Iron Deck (21)
Where does most iron reside in the body?
Ferrous (Fe2+) iron sits in porphyrin ring of Hb
What are the 3 compartments from which iron status is assessed?
Functional iron (bound to Hb)
Transport iron (bound to transferrin)
Stored iron (ferritin in liver)
How many binding sites are on transferrin for iron?
What does transferrin do?
Transport iron from donor tissue (macrophages, intestines, liver) to tissues (erythroid marrow)
What are holotransferrin and apotransferrin?
Holotransferrin: bound transferrin
Apotransferrin: unbound transferrin
Serum ferritin can also act as an acute phase protein. What is the implication of this?
Levels rise in infection, malignancy etc.
What are the intraluminal factors that affect iron absorption?
Haem iron easier to absorb
Reduction of ferric iron to ferrous iron
What are the 2 main mucosal iron transporters that affect iron absorption?
DMT-1 on mucosal surface
Ferroportin on serosal surface
What is hepcidin and what effect does it have on iron absorption?
Produced in liver in response to iron overload
Down-regulates ferroportin to decrease iron absorption
Where in the body does iron absorption/pick-up occur?
What are the consequences of a negative iron balance?
Epithelial changes (koilonychia, angular stomatitis)
List the main causes of iron deficiency
How does iron overload (haemochromatosis) arise? What effect does it have on erythroid marrow?
Increased ferritin storage with decreased iron release (due to hepcidin), resulting in iron overload and impaired iron supply to erythroid marrow
List some clinical features of hereditary haemochromatosis
Mutation in which gene accounts for 95% of hereditary haemochromatosis?
HFE gene encoding hepcidin
What are the diagnostic levels of serum ferritin for iron overload?
Over 300 micrograms/l in men
Over 200 micrograms/l in pre-menopausal women
When is a liver biopsy for haemochromatosis warranted?
If uncertain about iron overload
Assess tissue damage
How is hereditary haemochromatosis treated?
What is the typical cause of secondary iron overload?
Repeated blood transfusion
What is the treatment option for secondary iron overload?
Iron-chelating agents: desferrioxamine, deferiprone