Iron Flashcards
When RBCs are broken down, what stores the iron?
macrophages
Where does iron absorption mainly occur?
duodenum
What enhances iron absorption?
haem in meat
asorbic acid - reduces iron to Fe 2+ form
alcohol
What inhibits iron absorption?
tannins - tea
phylates - cereals, bran, nuts, seeds
calcium - dairy products
What is the role of duodenal cytochrome B?
reduces ferric iron Fe3+ to Fe2+
found on the luminal surface
What is the role of DMT?
transport ferrous iron into the duodenal enterocyte
What is the role of ferroportin?
facilitates iron export from the enterocyte and passes it to transferrin
What regulates iron absorption?
Hepcidin
What is the role of Hepcidin?
binds to ferroportin and degrades it meaning iron is trapped in the duodenal cells
When is Hepcidin upregulated?
more iron - more hepcidin produced
malignancy
infection
Where is Hepcidin produced?
liver
What are the two transferrin binding sites?
apo-transferrin - empty
holo-transferrin - full
Where in the body are there lots of transferrin receptors?
erythroid bone marrow
If there is iron deficiency, which transferrin binding site will be more abundant?
apo-transferrin
What is your maximum dietry iron absorption per day?
4-5mg
How does anaemia of chronic disease come about?
inflammatory cytokines cause increased synthesis of ferritin mRNA (increases storage)
increased hepcidin will degrade ferroportin mediated release of iron
this results in an impaired iron supply to marrow erythroblasts and eventually hypochromatic red cells
basically to starve bacteria of iron
What are the two types of iron overload?
primary - hereditary haemochromatosis
secondary - transfusional and iron loading anaemias
What is the problem with iron overload?
it ends up in tissues which causes oxidative harm
What is hereditary haemochromatosis?
HFE gene mutation - incomplete penetrance
decreased Hepcidin synthesis causing increased iron absorption
How does hereditary haemochromatosis present?
usually middle aged or later
iron overload >5g
non specific symptoms: weakness, fatigue, joint pains, impotence
long term: arthritis, cirrhosis, diabetes, cardiomyopathy
What are the diagnostic features of hereditary haemochromatosis?
transferrin saturation >50%
serum ferritin >300g/l in men or >200g/l in women
What is the treatment of hereditary haemochromatosis?
weekly venesection - want ferritin <20
screen first degree relatives
What causes secondary iron overload?
massive ineffective eryhropoeisis - B thala major, sideroblastic anaemia
refractory hypoplastic anaemias - bone marrow doesnt work - myelodysplasia and red cell aphasia
How is secondary iron overload treated?
iron chelating agents - desferrioxamine
