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Haematology > 9. Iron deficiency > Flashcards

9. Iron deficiency Flashcards

1
Q

Which proteins in the body require iron?

A
  • Ribonucleotide reductase
  • Haemoglobin
  • Myoglobin
  • Cyclo-oxygenase
  • Succinate dehydrogenase
  • Cytochrome a, b and c
  • Cytochrome P450
  • Catalase
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2
Q

Where is iron located in a red cell?

A
  • Iron is in the haem groups associated with globin chains of haemoglobin
  • Haem groups are near the surface of the molecule
  • Fe2+ (ferrous) state
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3
Q

How much iron do you need every day to re-make red cells and how is this done?

A
  • 20mg a day
  • Impossible to absorb this amount
  • Iron is recycled when red cells are broken down
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4
Q

How much iron do men and women need to absorb every day?

A
  • Men - 1mg a day

* Women - 2mg a day

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5
Q

How much iron does the normal human diet provide and why is this so different to the amount absorbed?

A
  • 12-15mg a day
  • Iron occurs in most natural foods e.g. fish, vegetables etc.
  • It is difficult to absorb iron - most that’s eaten is not absorbed
  • We can only absorb ferrous (fe2+) iron
  • Also depends what else you have in the meal that will depend the level of absorption e.g. orange juice helps increase Fe2+
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6
Q

Why is meat and fish a better source of iron in a diet?

A
  • Iron has already been incorporated into the haem group

* This is very easy to absorb

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7
Q

What 3 main factors affect the absorption of iron?

A
  • Diet: increase haem and ferrous iron
  • Intestine: acid in the duodenum
  • Systemic factors: iron deficiency, anaemia (increases absorption to compensate) etc.
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8
Q

How is iron absorbed?

A

1) Iron is absorbed from the gut lumen into the cells
2) Iron is transported by ferroportin
3) Hepcidin regulates ferroportin
4) Fe enters the blood and binds to transferrin

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9
Q

What is hepcidin and how does it work?

A
  • Peptide hormone - 25aa
  • If iron levels are high, hepcidin levels increase
  • Binds to and induces degradation of ferroportin
  • Iron is stuck in the enterocytes and lost from the body when these are shed
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10
Q

Where is ferroportin found?

A
  • Enterocytes of the duodenum
  • Macrophages of the spleen, which extract iron from old or damaged cells
  • Hepatocytes
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11
Q

How does transferrin work?

A
  • Holds onto Fe in the circulation
  • Only 20-40% saturated with iron
  • Forms stable complexes with iron and more than 40 other metal ions
  • Transferrin-iron interacts with the transferrin receptor and the whole complex is internalised
  • As the pH drops, iron is released and transferring receptors are recycled
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12
Q

How is iron kept soluble and non-toxic?

A

Iron proteins and transport systems maintain a soluble and non-toxic form

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13
Q

How does anaemia affect erythropoietin?

A
  • Anaemia
  • Tissue hypoxia
  • Increased erythropoietin production in the kidney (and liver)
  • Acts on red cell precursors
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14
Q

What is anaemia of chronic disease (ACD)?

A
  • Anaemia seen in people with a chronic infection
  • Condition causes stimulation of hepcidin, which decreases iron absorption
  • Erythropoiesis may also be reduced
  • No obvious cause
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15
Q

What are the laboratory signs of being ill (with an anaemic condition)?

A
  • C-reactive protein increases
  • Erythrocyte sedimentation rate increases - due to increased inflammatory proteins
  • Acute phases response increases
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16
Q

What are the associated conditions of ACD?

A
  • Chronic infections (TB/HIV)
  • Chronic inflammatory disorders (rheumatoid arthritis)
  • Underlying malignancy
  • Miscellaneous e.g. cardiac failure
17
Q

What causes ACD?

A 
• Underpinned by cytokine release in unwell patients
• Prevent the usual flow of iron from the duodenum to the red cells
• Include TNF alpha and interleukins
• Cytokines do several things:
- stop erythropoietin increasing
- stop iron flowing out of cells
- increase production of ferritin
- increase death of red cells
18
Q

Why does ACD make anaemia persistent than normal anaemia?

A
  • Normally, erythropoietin production increases to compensate for loss of haemoglobin
  • In ACD, erythropoietin production is blunted
19
Q

What is the most common cause of anaemia?

A

Iron deficiency

20
Q

What are 4 of the causes of iron deficiency?

A
  • Bleeding (most common) e.g. menstruation
  • Increased use by the body e.g. rapid growth, pregnancy
  • Dietary deficiency
  • Malabsorption
21
Q

When would you do a full GI investigation in someone with anaemia?

A
  • Patient is male

* Patient is a post-menopausal woman or has little menstrual loss

22
Q

What are the full GI investigations to check for bleeding?

A

• Gastroscopy
• Duodenal biopsy
• Colonoscopy
• If there are no GI abnormalities in the above, look at the small bowel (unusual for this to occur)
- give a small bowel meal (radio-opaque substance) and follow through
• Can also check for anti-helicobacter antibodies and anti-coeliac antibodies (ultrasound on kidneys, urine dipstick)

23
Q

Which laboratory parameters should you look at in someone who is iron deficient?

A
  • MCV
  • Serum iron
  • Ferritin
  • Transferrin
  • Transferrin saturation
24
Q

What are the 3 causes of a low MCV?

A
  • Iron deficiency
  • Thalassaemia trait (heterozygous)
  • Anaemia of chronic disease (low or normal MCV)
25
Q

Why is a low MCV and low serum iron not enough to tell if a patient is iron deficient?

A

This can also be seen in ACD

26
Q

If a patient has iron deficiency but normal ferritin, what could this mean?

A

There is a chronic underlying disease

• check CRP and ESR to check for iron deficiency in this case

27
Q

If a patient had low Hb (anaemic), low serum iron and low ferritin, does this patient have iron deficiency, and what else could be checked to confirm this?

A
  • Yes

* A low transferrin saturation would confirm this

28
Q 
What are the levels of the following in classic iron deficiency:
• Hb
• MCV
• Serum iron
• Ferritin
• Transferrin
• Transferrin saturation
A
  • Hb - low
  • MCV - low
  • Serum iron - low
  • Ferritin - low
  • Transferrin - high
  • Transferrin saturation - low
29
Q 
What are the levels of the following in classic anaemia of chronic disease:
• Hb
• MCV
• Serum iron
• Ferritin
• Transferrin
• Transferrin saturation
A
  • Hb - low
  • MCV - normal/low
  • Serum iron - low
  • Ferritin - normal/high
  • Transferrin - normal/low
  • Transferrin saturation - normal
30
Q 
What are the levels of the following in the classic thalassaemia trait:
• Hb
• MCV
• Serum iron
• Ferritin
• Transferrin
• Transferrin saturation
A
  • Hb - low
  • MCV - low
  • Serum iron - normal
  • Ferritin - normal
  • Transferrin - normal
  • Transferrin saturation - normal
31
Q 
What are the levels of the following in rheumatoid arthritis with a bleeding ulcer:
• Hb
• MCV
• Serum iron
• Ferritin
• Transferrin
• Transferrin saturation
A
  • Hb - low
  • MCV - low
  • Serum iron - low
  • Ferritin - normal
  • Transferrin - high
  • Transferrin saturation - low
32
Q

Describe a blood film in someone with iron deficiency

A
  • Very pale cells - not much haemoglobin

* Pencil cells can be seen (long and thin)

Haematology (11 decks)

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