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Haematology > Iron in Health and Disease > Flashcards

Iron in Health and Disease Flashcards

1
Q

What is iron present in throughout the body?

A

Haemoglobin
Myoglobin
Enzymes eg cytochromes

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2
Q

Why is iron important?

A

Used for oxygen transport - haemoglobin

Electron transport eg mitochondrial production of ATP

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3
Q

Why can iron be dangerous?

A

It contributes to oxidative stress but cannot be actively excreted from the body

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4
Q

what adaptive mechanisms are there

A

Safe transport
safe storage
regulation of iron absoption

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5
Q

What is oxidative stress?

A

Oxidative stress reflects an imbalance between the systemic manifestation of reactive oxygen species and a biological system’s ability to readily detoxify the reactive intermediates or to repair the resulting damage.

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6
Q

Where is most of the iron in the body

A

In haemoglobin

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7
Q

Describe the structure of haemoglobin

A

Four haem groups in a globin chain.

Haem group made up of iron sitting in a prophyrin ring.

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8
Q

How is the haem group made

A

Iron and protoporphyrin come together in the mitochondria to make haem which is deposited in the cytoplasm

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9
Q

What assesses functional iron

A

Hb concentration

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10
Q

What assesses transport iron/iron supply to the tissues

A

Percentage saturation of transferrin with iron

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11
Q

What assesses storage iron

A 
serum ferritin
tissue biopsy (bone marrow for iron deficiency; liver for iron overload)
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12
Q

What is the function of transferrin.

A

Transports iron from donor tissues (macrophages, intestinal cells and hepatocytes) to tissues expressing transferrin receptors (erythroid marrow).
It has two binding sites for iron atoms.

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13
Q

How is the percentage saturation of transferrin measured and what does it indicate

A

Serum iron/transferrin x 100

  • measures iron supply
  • reflects proportion of diferric transferrin
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14
Q

How is iron absoption regulated

A

Intraluminal factors - solubility of inorganic iron, reduction of ferric to ferrous.
Mucosal factors - expression of iron transporters (DMT-1) at mucosal surface and ferroportin at serosal surface
Systemic factors- hepcidin

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15
Q

Why is it important that ferric iron is reduced to ferrous iron to be absorbed

A

ferric iron is insoluble and must be reduced to ferrous before crossing the bowel lumen

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16
Q

why is hepcidin important in the regulation of iron absoption

A

Hepcidin is produced in the liver in response to iron load and inflammation.
It down regulates ferroportin

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17
Q

What is ferroportin

A

It is a transmembrane protein that regulates the exit of iron from enterocytes and macrophages. Where is is then passed on to transferrin and transported elsewhere.

18
Q

What do DMT1 transporters do

A

Transports iron into the duodenal enterocyte

19
Q

How much iron do we need?

A

About 4g in an adult

2-5g can be normal depending on the adult and circumstances

20
Q

What are the three main groups of disorders of iron metabolism

A

Iron deficiency
Iron malutilisation
iron overload

21
Q

what type of anaemia is caused be iron malutilisation

A

Anaemia of chronic disease (which can be microcytic or normocytic)

22
Q

What is the mechanism of anaemia of chronic disease?

A
  1. Increased transcription of ferritin mRNA occurs due to stimulation by inflammatory cytokines –> ferritin synthesis increases
  2. Increases plasma hepcidin (due to increases ferritin) blocks ferroportin-mediated release of iron from cells
  3. Results in impaired iron supply to marrow erythroblasts and eventually hypochromic red cells

In a nutshell = iron is trapped in cells

23
Q

What are the blood measurements of iron in anaemia of chronic disease

A

Ferritin = high/normal
Transferrin= low
Serum transferrin receptors = low

24
Q

what is primary iron overload

A

Long term excess iron absorption with parenchymal rather than macrophage iron loading and eventual organ damage

25
Q

What groups of patients does iron overload occur in

A
  1. those who chronically absorb increased quantities of iron

2. those recieving repeated blood transfusions to treat conditions such as thalassaemia, aplastic anaemia

26
Q

What is hereditary haemochromatosis

A

A condition in which iron absorption from a normal diet is inappropriately increased from birth
It an is inherited conditon

27
Q

what is the mode of inheritance of haemochromatosis

A

autosomal recessive

28
Q

What are the clinical features of hereditary haemochromatosis

A 
Weakness/fatigue
joint pain
impotence
arthritis
cirrhosis
diabetes
cardiomyopathy

Usually presents in middle age or later with iron overload >5mg

29
Q

What gene is mutated in herediatory haemochromatosid

A

HFE gene
Main effect likely to be via reduced hepcidin synthesis
Accounts for 95 percent of cases
Incomplete penetrance

30
Q

How is hereditary haemochromatosis diagnosed

A

Genes - HFE
Phenotype-
Transferrin sats more than fifty percent
serum ferritin more than 300ug in men or 200 in premenpausal women
Liver biopsy only if uncertain or to asses tissue damage

31
Q

what is the treatment of haemochromatosis?

A

weekly phlebotomy (450-500ml, 200-250ml of iron)
Initial aim to exhaust iron stored (ferritin less than 20ug)
Therefore keep ferritn below 50ug

32
Q

What are possible complications of haemochromatosis

A 
Diabetes
infection
Cardiac failure
Hepatic failure
Varices
Hepatoma
33
Q

What is the most common cause of death after the introduction of phlebotomy in pts with haemochromatosis

A

Hepatoma

34
Q

What is the risk for first degree relatives of pts with hereditaoty haemochromatosis

A

1 in 4

35
Q

Why is family screening important

A

Haemochromatosis may be asymptomatic until irreversible organ damage has occurred.

36
Q

What is secondary iron overload

A

Overload due to treatment for anaemias

37
Q

What is the cause of secondary iron overload

A

Repeated red cell transfusions

excessive iron absoption related to over-actve erythropoiesis

38
Q

What disorders can iron-loading anaemias (iron overload) occur in

A

Thalassaemias and sideroblastic anaemia - due to massive ineffective erythropoiesis
Red cell aplasia and myelodysplasia - refractory hypoplastic anaemias

39
Q

How much iron is in a unit of blood usually

A

200-250mg

40
Q

What can result from iron overload

A

Damage to liver, heart and endocrine glands

41
Q

What is the treatment for secondary iron overload

A

Treatment by venesection NOT an option in already anaemic patients

Iron chelatin drugs are used

42
Q

Name iron chelating drugs

A

Desferrioxamine (sc or iv)

New oral agents - deferoprone, deferasirox

Haematology (21 decks)

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