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Haematology > Anaemia: Biochemistry > Flashcards

Anaemia: Biochemistry Flashcards

1
Q

how can iron status be tested?

A

functional iron= Hb
transported iron= serum transferrin
storage= serum ferritin

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2
Q

what is normal transferrin saturation?

A

20-50%

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3
Q

define holotransferrin

A

iron bound to tranferrin

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4
Q

what is apotransferrin?

A

unbound transferrin

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5
Q

what is transferrin?

A

a protein with two binding sites for iron atoms

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6
Q

function of transferrin

A

transports from donor tissues to tissues expressing transferrin receptors

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7
Q

donor tissues

A

macrophages
intestinal cells
hepatocytes

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8
Q

what tissues express transferrin receptors?

A

erythroid marrow

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9
Q

when is saturation of transferrin reduced?

A

iron deficiency

anaemia of chronic disease

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10
Q

when is saturation of transferrin increased?

A

haemochromatosis

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11
Q

what does ferritin store?

A

4000 ferric ions (Fe3+)

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12
Q

what is ferritin?

A

large intracellular protein that is spherical

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13
Q

why are tiny amounts of ferritin present in the serum?

A

reflects ferritin synthesis in response to iron status of host

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14
Q

what does serum ferritin also act as?

A

acute phase protein

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15
Q

what causes serum ferritin to increase (acute phase protein)

A

infection
malignancy
liver injury

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16
Q

two forms of iron

A

ferric (Fe3+)

ferrous (Fe2+)

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17
Q

is there a mechanism for iron excretion?

A

no

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18
Q

what enhances absorption of iron?

A

dedicated haem iron transporter
ascorbic acid (reduces iron to Fe2+)
alcohol

19
Q

what inhibits iron absorption (food examples)?

A

tannins (tea)
phytates (cereals, bran, nuts, seeds)
calcium (dairy products)

20
Q

mechanisms of iron absorption

A

duodenal cytochrome B
DMT-1
ferroportin

21
Q

role of duodenal cytochrome B

A

reduces Fe3+ to Fe2+

22
Q

role of DMT-1

A

transports ferrous iron into duodenal enterocyte

23
Q

role of ferroportin

A

facilitates iron export from enterocytes and passed to transferrin

24
Q

what regulates iron absorption?

A

hepcidin

25
Q

what produces hepcidin?

A

liver

26
Q

what causes hepcidin to be produced?

A

increased iron load

inflammation

27
Q

action of hepcidin

A

binds to ferroportin causing its degradation so iron is trapped in duodenal cells and macrophages

28
Q

what causes hepcidin levels to decrease?

A

iron deficiency

29
Q

consequences of iron deficiency

A

low ferritin
low MCV
microcytic anaemia
epithelial changes (skin, koilonychia and angular cheilitis)

30
Q

causes of iron deficiency

A

diet insufficiency
losing too much blood
not absorbing enough

31
Q

causes of diet insufficiency of iron intake

A

vegetarian diets

32
Q

causes of blood loss

A 
menorrhagia
GI tumours
occult
ulcer
NSAIDs
haematuria
33
Q

causes of lack of absorption

A

Coeliac’s

achlorhydria (vitamin C needed to absorb iron)

34
Q

describe the macrophage iron block in inflammation

A

ferritin synthesis increased
increased hepcidin reducing iron release
decrease iron for erythroblasts

35
Q

what is the macrophage iron block for?

A

protective mechanism as microorganisms like iron

36
Q

what are B12 and folate?

A

co-factors in maturation of blood cells and nervous system

37
Q

where is B12 found?

A

animal food products

38
Q

digestion of B12

A

acid in the stomach allows it to bind to intrinsic factor from gastric parietal cells
alkaline environment activates it
travels to jejunum/ileum before entering bloodstream

39
Q

where are dietary folates found?

A

plant foods

40
Q

absorption of folates

A

converted to monoglutamate and absorbed in jejunum

41
Q

causes of B12 and folate deficiency

A 
alcoholics
Coeliac's
Crohn's
haemolysis
pregnancy
malignancy
anticonvulsants
42
Q

body stores of B12

A

2-4 years

43
Q

body stores of folate

A

4 months

44
Q

daily requirements of B12 and folate

A 
B12= 1.5ug/day
folate= 200ug/day

Haematology (34 decks)

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