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3 HAEM > IRON > Flashcards

IRON Flashcards

1
Q

why is safe storage and transport of iron important

A

can cause inflammation and organ damage due to oxidative stress and free radical production

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2
Q

where does the majority of iron absorption occur

A

duodenum

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3
Q

what dietary factors enhance iron absorption

A

haem iron is more readily absorbable than non-haem iron (eg red meats)
ascorbic acid (vitamin C)
alcohol

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4
Q

what dietary factors inhibit iron absorption

A

tannins eg tea
phytates eg cereals, bran, nuts and seeds
calcium

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5
Q

in which state must iron ions exist in order to be absorbed

A

Fe2+

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6
Q

which enzyme is responsible for converting ferric to ferrous iron for absorption

A

duodenal cytochrome B

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7
Q

what is the function of DMT-1

A

transports ferrous iron into the duodenal enterocyte

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8
Q

what is the function of ferroportin

A

facilitates iron export from the enterocytes

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9
Q

which protein binds to iron for transport

A

transferrin

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10
Q

what is hepcidin

A

negative regulatory of iron uptake

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11
Q

how is iron absorption regulated

A

hepcidin binds to ferroportin causing its degradation

this prevents iron from leaving the cells so serum iron reduces

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12
Q

where is hepcidin produced

A

in the liver

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13
Q

what causes production of hepcidin

A

iron load and inflammation

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14
Q

in which form should iron be to bind to transferrin

A

fe3+

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15
Q

which enzyme is needed to convert Fe2+ to Fe3+ for transport

A

haphaestin

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16
Q

what are the 3 compartments assessed in iron status

A 
functional iron (Hb)
transport iron (% saturation of transferrin)
storage iron (ferritin)
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17
Q

how many iron binding sites are there on transferrin molecules

A

2

18
Q

which tissues are especially rich in transferrin receptors

A

erythroid marrow

19
Q

what is a normal level of transferrin saturation

A

20-50%

20
Q

what happens to transferrin saturation in iron overload

A

elevates

21
Q

what happens to transferrin saturation in iron deficiency

A

decreases

22
Q

how many iron ions can a ferritin molecule store

A

4000

23
Q

what form of iron is stored in ferritin

A

Fe3+

24
Q

in which cases, other than iron overload, might ferritin go up and why

A

it is an acute phase protein so may rise in infection, malignancy etc

25
Q

how can iron deficiency be confirmed

A

combination of anaemia (decreased Hb iron) and reduced storage iron (low serum ferritin)

26
Q

what are causes of iron deficiency

A

insufficient intake to meet physiological demand
losing too much
not absorbing enough

27
Q

what are common causes of chronic blood loss

A

menorrhagia
GI bleeding (tumours, ulcers, parasitic infection)
haematuria

28
Q

what causes anaemia of chronic disease

A

increased ferritin synthesis and increased plasma hepcidin promotes iron storage and prevents iron transport

29
Q

what causes primary iron overload

A

haemochromatosis

30
Q

why does haemochromatosis cause iron overload

A

decreases synthesis of hepcidin resulting in increased absorption of iron

31
Q

clinical features of haemochromatosis

A 
weakness/fatigue 
joint pains 
impotence 
arthritis 
cirrhosis 
diabetes 
cardiomyopathy
32
Q

when does haemochromatosis usually present

A

middle age or later

when iron overload >5 g

33
Q

mutations in which gene are usually the cause of haemochromotosis

A

HFE gene

2 different mutations

34
Q

how is haemochromatosis usually diagnosed

A

transferrin saturation >50%
serum ferritin >300 ug/L (men) or >200 ug/L (pre-menopausal women)
liver biopsy/imaging for evidence of cirrhosis

35
Q

what is the treatment for haemochromatosis

A

initial treatment with weekly venipuncture (450-500 ml) until ferritin <20 ug/L
thereafter maintenance to keep ferritin <50 ug/L

36
Q

what is the most common cause of mortality in haemochromatosis

A

hepatoma/liver disease

37
Q

why is it safe to wait to screen children with parents with haemochromatosis until they are adults

A

because iron overload is gradual and won’t become pathologic until they are middle aged

38
Q

causes of secondary iron overload

A

repeated red cell transfusions

excessive iron absorption due to overactive erythropoiesis

39
Q

which disorders are treated with repeated red cell transfusions, and therefore increase the risk of iron overload

A

Thalassaemia
siderblastic anaemia
red cell aplasia
myelodysplasia

40
Q

how is secondary iron overload treated

A

iron chelating agents
desferrioxamine (SC/IV)
deferiprone/deferasirox (PO)

41
Q

why is venesection not a suitable treatment for secondary iron overload

A

the patients are already anaemia

3 HAEM (20 decks)

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