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Haematology > Week 1- iron in health and disease > Flashcards

Week 1- iron in health and disease Flashcards

1
Q

Why is iron essential?

A

For oxygen transport

For electron transport e.g. mitochondrial production of ATP

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2
Q

Where is iron found?

A

Haemoglobin
Myoglobin
Enzymes

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3
Q

Why is iron dangerous?

A

Its chemical reactivity can cause oxidative damage to cells.

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4
Q

Where is most of the bodies iron found?

A

In haem

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5
Q

How much iron is needed to be taken in (eaten) each day?

A

1mg

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6
Q

How much iron is in the plasma?

A

4mg

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7
Q

How is iron constantly recycled? (Describe the cycle).

A

In the plasma, gets into the erythroid marrow, is incorporated into the red cell haemoglobin, then ingested by macrophages when Hb dies so is in the macrophage store, and repeat.

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8
Q

Where does most of iron absorption occur?

A

Mainly takes place in the duodenum.

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9
Q

Which cells absorb iron?

A

Duodenal enterocytes

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10
Q

Which protein transports iron into the duodenual enterocyte?

A

Divalent metal transporter (DMT-1)

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11
Q

Which protein transports iron out of the duodenal enterocyte into the rest of the body?
What protein does it then pass iron onto?

A

Ferroportin gets the iron out of the duodenal enterocyte and passes it on to transferrin which transports iron round the rest of the body.

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12
Q

Which protein down regulates iron?

A

Hepcidin blocks the ferroportin protein stopping iron from moving from the duodenal enterocyte to the rest of the body.

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13
Q

How can iron absorption be regulated?

A

Intraluminal factors- e.g. acidic environment aids iron absorption, haem iron is easier to absorb, reduction of ferric to ferrous (fe2+)
Mucosal factors- expression of DMT-1, ferroportin at serial surface
Systemic factors- hepcidin presence

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14
Q

What is meant by functional iron?

A

The iron in haemoglobin.

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15
Q

What is transferrin?

What is its function?

A

The major iron transport protein.

Takes iron from donor tissues (e.g. enterocytes, macrophages) to tissues expressing transferrin receptors.

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16
Q

What is transferrin’s structure?

A

It is a protein with two binding sites for iron.

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17
Q

What is the main tissue rich in transferrin receptors?

A

Erythroid marrow.

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18
Q

What does measuring transferrin saturation give you an indication of?

A

Iron supply (basically how many of the binding sites of transferrin are actually occupied with iron).

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19
Q

What is the name for iron bound to transferrin?

What is the name for iron unbound to transferrin?

A

Holotransferrin- bound

Apotransferrin- unbound.

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20
Q

What is the normal transferrin saturations?

A

20-50%.

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21
Q

If you have iron overload, what happens to the transferrin saturations?

A

They increase.

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22
Q

If you have iron deficiency, what happens to transferrin saturations?

A

They decrease.

23
Q

How can you assess storage iron?

A

Two ways to look at this:
Serum ferritin
Biopsy (rarely).

24
Q

Describe the structure of ferritin?

A

Large protein shell that can store up to 4000 iron ions (Fe3+)

25
Q

Why do we measure serum ferritin?

A

It tends to reflect the amount of stored iron.

26
Q

In what situations may serum ferritin increase?

A

Increase in iron storage

However it can also go up in malignancy or infection,

27
Q

In iron deficiency, what would you expect the ferritin levels to be like?

A

Low.

28
Q

What is the normal total body iron in an adult?

A

About 4g.

29
Q

What occurs in the body if you have a negative iron balance? (I.e. you are not taking in as much iron as you need)?

A

You will exhaust your iron stores
Iron deficient erythropoiesis will occur resulting in microcytic anaemia
Also get epithelial changes- koilonychia (spooning of nails), angular stomatitis (dry bits at corners of the mouth).

30
Q

What does hypo chromic microcytic anaemia suggest?

A

Deficient haemoglobin synthesis- makes the cells small and hypochromic (lacking in colour).

31
Q

What can a deficient haemoglobin synthesis be due too? (think about the things that make up Hb)

A

Haem synthesis- iron deficiency, anaemia of chronic disease

Globin chains- thalassaemias.

32
Q

What two factors do you need to diagnose iron deficiency?

A

Combination of anaemia (decreased Hb iron)
and
Reduced storage iron (low serum ferritin)

33
Q

What are the causes of iron deficiency?

A

Bleeding
Not absorbing enough (coeliacs)
Dietary- children and women due to greater requirements.
Pregnancy.

34
Q

When thinking of iron deficiency, it is good to look for a cause. What might be the causes of chronic blood loss that can lead to iron deficiency?

A

Menorrhagia
GI causes- tumours, ulcers, NSAIDs, parasitic infections
Haematuria

35
Q

In occult blood loss, iron is lost in small amounts per day. What amount of blood do you have to lose to become iron deficient?

A

8-10mls mean you lose 4-5mg of iron per day (which is your daily intake meaning you will become iron deficient)

36
Q

What is anaemia of chronic disease also known as?

A

Iron malutlisation.

37
Q

What normally happens to a red cell once its reached the end of its lifespan?

A

Normally broken down into its constituents- haem and globin. The globin chains are broken down into amino acids. The haem porphyrin ring is made into bilirubin and excreted and the iron is recycled. Some of it will go on to ferritin as storage iron, but most will be taken by transferrin to the marrow erythrocytes.

38
Q

In anaemia of chronic disease, what happens to the red blood cells when they are broken down?

A

Inflammatory cytokines cause an increase in iron that is stored as ferritin.
Also get increased hepcidin levels which stop ferroportin release of iron (means transferrin can’t then bind also).

39
Q

In anaemia of chronic disease, what happens to the red blood cells when they are broken down?

A

Inflammatory cytokines cause an increase in iron that is stored as ferritin.
Also get increased hepcidin levels which stop ferroportin release of iron (means transferrin can’t then bind also).
This results in a reduced iron supply to the bone marrow and eventually hypo chromic microcytic red cells.

40
Q

How can iron overload be classified?

A

As primary- e.g. hereditary haemochromatosis

Or secondary- transfusional, iron loading anaemias.

41
Q

What occurs in primary iron overload?

A

Gradual, long term excess iron with progressive parenchymal (iron is laid down in the tissues) rather than macrophage iron loading.

42
Q

Where is the mutation in hereditary haemochromatosis?

A

HFE gene.

43
Q

What occurs in hereditary haemochromatosis?

A

Decreases synthesis of hepcidin, therefore iron absorption is not down-regulated. This results in gradual iron accumulation in tissues.

44
Q

What clinical features can someone with hereditary haemochromatosis present with?

A

Weakness, fatigue, joint pains, impotence.

Also other things like diabetes, cardiomyopathy, cirrhosis, arthritis.

45
Q

When do people present with hereditary haemochromatosis?

A

Usually presents at middle age.

46
Q

What results would you expect to find it someone with HH?

A 
Ferritin raised >300
Transferrin raised (>50%)
Hb- normal
47
Q

What investigations will you do in HH?

A

Look at normal bloods
Exclude other causes e.g. liver cirrhosis.
Then look for HFE gene (95%) of cases

48
Q

Which two mutations are routinely screened for in HH?

A

C282y
H63D

NOTE- there are also mutations in other iron proteins e.g. transferrin, that can cause similar issues, however very rare.

49
Q

How do you treat haemachromatosis? What is the aim of this?

A

You basically bleed the patient (venesection), which removes haemoglobin and therefore iron. This is done weekly.
The aim is to exhaust the iron stores. Once this has occurred (ferritin is very low), stop venesection them weekly. Then maintenance venesection (3-4 times yearly)

50
Q

If a patient has liver cirrhosis due to iron overload, what are they at increased risk of?

A

Hepatocellular carcinoma

51
Q

Who do you screen for haemochromatosis?

A

First degree relatives of someone who is diagnosed. Don’t test children until they are adults.

52
Q

What secondary causes can cause iron overload?

A

repeated transfusions, each transfusion has about 250-300mg of iron. Repeated transfusions due to chronic anaemia, and anaemia itself causes the body to upregulate iron absorption.

53
Q

How can you treat secondary iron overload?

A

Cant do venesection as they are already anaemic

So you have to give them iron chelating drugs-desfarrioxamine

Haematology (26 decks)

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