Iron in Health and Disease Flashcards
Why can iron be dangerous?
It causes oxidative stress and produces free radicals
The majority of body iron can be found within where?
Within the haem group, in globulin chains. The Fe2+ ion sits specifically within the porphyrin ring
Where is Hb synthesised? What two components are needed to form haem?
In the cytoplasm of immature blood cells / protoporphyrin and Fe2+
What is the rate of a) iron absorption? b) iron loss? / what is the significance of this?
a) 1mg/day b) 1mg/day / keeps a constant level of iron in the body
When iron is absorbed, it is taken into the plasma. From the plasma, it can travel to where?
The parenchymal tissues (predominantly the liver) to be stored, or to the erythroid marrow to make haem
When red cells are broken down, where is iron taken into to be taken back to the plasma?
Macrophage stores
All iron in the plasma is bound to what molecule? This iron in the plasma acts as what?
Transferrin / available iron
Iron absorption occurs mainly where? Therefore it is absorbed into where?
The duodenum / epithelial cells of the duodenal mucosa
What are some factors which enhance iron absorption?
Ascorbic acid and alcohol
What are some factors which decrease iron absorption?
Tannins, Ca++, PPI drugs
Which iron state is more readily absorbed?
Fe2+
What is the first molecule involved in the absorption of iron, which is found in the duodenal luminal surface? What is its function?
Duodenal cytochrome B - reduces the ferric ion (Fe3+) to the ferrous ion (Fe2+)
What is the role of divalent metal transporter 1 in the absorption of iron?
Transports ferrous iron from the duodenal lumen to the duodenal enterocyte
What is the role of ferroportin in iron absorption?
Facilitates iron export from cells and passes it onto transferrin for transport elsewhere
Iron absorption is mainly regulated by which molecule? Where is most of this produced? In response to what?
Hepcidin / liver / iron load and inflammation
How does hepcidin negatively regulate iron uptake?
It binds to ferroportin and causes its degradation so that iron is ‘trapped’ inside macrophages and duodenal enterocytes
The liver is the main sensor of iron. If there is plentiful iron, what will it do?
Produce hepcidin to downregulate ferroportin
The liver is the main sensor of iron. If there is iron deficiency, what will it do?
Inhibit hepcidin production to upregulate ferroportin
What is transferrin?
A protein with two binding sites for iron atoms in the Fe3+ state
What is the role of transferrin?
Transports iron from donor tissues (e.g. macrophages, duodenal intestinal cells and hepatocytes) to cells expressing transferrin receptors (mainly the erythroid marrow)
Describe what is meant by each of the following terms: a) holotransferrin? b) apotransferrin?
a) transferrin bound to iron b) transferrin not bound to iron
What happens to transferrin saturation if someone is in iron overload?
Increase
What happens to transferrin saturation if someone is iron deficienct?
Decrease
What is ferritin?
A spherical intracellular protein which stores up to 4000 Fe3+ ions
A tiny amount of serum ferritin reflects the intracellular ferritin synthesis which acts as an indirect measure of what?
Storage iron
What are some other factors (aside from excess iron) which can cause serum ferritin levels to rise?
It is an acute phase protein so can be risen in infection or malignancy
What happens to serum ferritin in iron deficiency?
Decreased
What happens to serum ferritin in iron overload?
Increased
In terms of assessment of iron status, what is used as a measure of functional iron?
Hb concentration
In terms of assessment of iron status, what is used as a measure of transport iron?
% saturation of transferrin with iron
In terms of assessment of iron status, what is used as a measure of storage iron?
Serum ferritin (and also tissue biopsy but this is rarely indicated)
