IRON

Question 1

why is safe storage and transport of iron important

Answer 1

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

Question 2

where does the majority of iron absorption occur

Answer 2

duodenum

Question 3

what dietary factors enhance iron absorption

Answer 3

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

Question 4

what dietary factors inhibit iron absorption

Answer 4

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

Question 5

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

Answer 5

Fe2+

Question 6

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

Answer 6

duodenal cytochrome B

Question 7

what is the function of DMT-1

Answer 7

transports ferrous iron into the duodenal enterocyte

Question 8

what is the function of ferroportin

Answer 8

facilitates iron export from the enterocytes

Question 9

which protein binds to iron for transport

Answer 9

transferrin

Question 10

what is hepcidin

Answer 10

negative regulatory of iron uptake

Question 11

how is iron absorption regulated

Answer 11

hepcidin binds to ferroportin causing its degradation

this prevents iron from leaving the cells so serum iron reduces

Question 12

where is hepcidin produced

Answer 12

in the liver

Question 13

what causes production of hepcidin

Answer 13

iron load and inflammation

Question 14

in which form should iron be to bind to transferrin

Answer 14

fe3+

Question 15

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

Answer 15

haphaestin

Question 16

what are the 3 compartments assessed in iron status

Answer 16

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

Question 17

how many iron binding sites are there on transferrin molecules

Answer 17

2

Question 18

which tissues are especially rich in transferrin receptors

Answer 18

erythroid marrow

Question 19

what is a normal level of transferrin saturation

Answer 19

20-50%

Question 20

what happens to transferrin saturation in iron overload

Answer 20

elevates

Question 21

what happens to transferrin saturation in iron deficiency

Answer 21

decreases

Question 22

how many iron ions can a ferritin molecule store

Answer 22

4000

Question 23

what form of iron is stored in ferritin

Answer 23

Fe3+

Question 24

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

Answer 24

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

Question 25

how can iron deficiency be confirmed

Answer 25

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

Question 26

what are causes of iron deficiency

Answer 26

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

Question 27

what are common causes of chronic blood loss

Answer 27

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

Question 28

what causes anaemia of chronic disease

Answer 28

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

Question 29

what causes primary iron overload

Answer 29

haemochromatosis

Question 30

why does haemochromatosis cause iron overload

Answer 30

decreases synthesis of hepcidin resulting in increased absorption of iron

Question 31

clinical features of haemochromatosis

Answer 31

``` weakness/fatigue joint pains impotence arthritis cirrhosis diabetes cardiomyopathy ```

Question 32

when does haemochromatosis usually present

Answer 32

middle age or later | when iron overload >5 g

Question 33

mutations in which gene are usually the cause of haemochromotosis

Answer 33

HFE gene | 2 different mutations

Question 34

how is haemochromatosis usually diagnosed

Answer 34

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

Question 35

what is the treatment for haemochromatosis

Answer 35

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

Question 36

what is the most common cause of mortality in haemochromatosis

Answer 36

hepatoma/liver disease

Question 37

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

Answer 37

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

Question 38

causes of secondary iron overload

Answer 38

repeated red cell transfusions | excessive iron absorption due to overactive erythropoiesis

Question 39

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

Answer 39

Thalassaemia siderblastic anaemia red cell aplasia myelodysplasia

Question 40

how is secondary iron overload treated

Answer 40

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

Question 41

why is venesection not a suitable treatment for secondary iron overload

Answer 41

the patients are already anaemia