Iron in health and disease Flashcards
Where is the majority of body iron found?
Haem
Haem groups are found where?
In global chains
Which iron ion is present in haem?
Fe2+ (ferrous ion)
What is haem made up of?
Protoporphyrin ring + Fe
Porphyyrin ring + Fe3+ -> haem
Where in the global chain do iron ions sit?
Fe2+, ferrous ion, sits in the porphyrin ring
Where is iron absorbed?
duodenum
Name the membrane proteins involved in iron absorption and their actions
DMT-1 (divalent metal transporter) - transports iron into the duodenal enterocyte.
Ferroportin - facilitates iron export from the enterocyte.
Trensferrin - receives iron from ferroportin to transport elsewhere.
Hepcidin - down-regulates ferroportin
Which types of factors regulate iron absorption?
Intraluminal
Mucosal
Systemic
What are the intraluminal factors?
Solubility of inorganic iron,
Haem iron easier to absorb,
Reduction of ferric (2+) to ferrous (3+).
What are the mucosal factors?
(expression of iron transporters)
DMT-1 at mucosal surface
Ferroportin at serial surface
What are the systemic factors?
Hepcidin - the major negative regulator of iron uptake.
Produced in the liver in response to iron load and inflammation.
Down-regulates ferroportin - iron is ‘trapped’ in duodenal cells and macrophages.
What are the 3 compartments of iron status assessment?
Functional iron, Transport iron/supply to tissues, and storage iron.
What determines the functional iron compartment?
Haemoglobin concentration
How many iron binding sites does transferrin have?
2
Describe the role of transferrin.
Transports iron from donor tissues (macrophages, intestinal cells, hepatocytes) to tissues expressing transferrin receptors.
Name a tissue rich in transferrin receptors.
Erythroid marrow - bone marrow producing RBCs.
What is measured to determine iron supply? And how is this done?
transferrin saturation;
- serum iron/total iron binding capacity (to transferrin) x100%
- reflects the proportion of diferric transferrin
= % saturation of transferrin with iron.
Normal transferrin saturation?
20-50%
Name for iron bound to transferrin?
Holotransferrin
Unbound transferrin name?
Apotransferrin
What is the storage compartment of iron status?
Storage iron:
Serum ferritin & tissue biopsy (rarely needed)
What is ferritin?
A serum intracellular protein which stored up to 4000 ferric ions (Fe3+)
What is an indirect measure of storage iron?
A tiny amount of serum ferritin reflects intracellular ferritin synthesis.
Examples of when serum ferritin would be raised.
Infection, malignancy, liver injury - it acts as an acute phase protein
