Iron

Question 1

When RBCs are broken down, what stores the iron?

Answer 1

macrophages

Question 2

Where does iron absorption mainly occur?

Answer 2

duodenum

Question 3

What enhances iron absorption?

Answer 3

haem in meat
asorbic acid - reduces iron to Fe 2+ form
alcohol

Question 4

What inhibits iron absorption?

Answer 4

tannins - tea
phylates - cereals, bran, nuts, seeds
calcium - dairy products

Question 5

What is the role of duodenal cytochrome B?

Answer 5

reduces ferric iron Fe3+ to Fe2+

found on the luminal surface

Question 6

What is the role of DMT?

Answer 6

transport ferrous iron into the duodenal enterocyte

Question 7

What is the role of ferroportin?

Answer 7

facilitates iron export from the enterocyte and passes it to transferrin

Question 8

What regulates iron absorption?

Answer 8

Hepcidin

Question 9

What is the role of Hepcidin?

Answer 9

binds to ferroportin and degrades it meaning iron is trapped in the duodenal cells

Question 10

When is Hepcidin upregulated?

Answer 10

more iron - more hepcidin produced
malignancy
infection

Question 11

Where is Hepcidin produced?

Answer 11

liver

Question 12

What are the two transferrin binding sites?

Answer 12

apo-transferrin - empty

holo-transferrin - full

Question 13

Where in the body are there lots of transferrin receptors?

Answer 13

erythroid bone marrow

Question 14

If there is iron deficiency, which transferrin binding site will be more abundant?

Answer 14

apo-transferrin

Question 15

What is your maximum dietry iron absorption per day?

Answer 15

4-5mg

Question 16

How does anaemia of chronic disease come about?

Answer 16

inflammatory cytokines cause increased synthesis of ferritin mRNA (increases storage)
increased hepcidin will degrade ferroportin mediated release of iron
this results in an impaired iron supply to marrow erythroblasts and eventually hypochromatic red cells
basically to starve bacteria of iron

Question 17

What are the two types of iron overload?

Answer 17

primary - hereditary haemochromatosis

secondary - transfusional and iron loading anaemias

Question 18

What is the problem with iron overload?

Answer 18

it ends up in tissues which causes oxidative harm

Question 19

What is hereditary haemochromatosis?

Answer 19

HFE gene mutation - incomplete penetrance

decreased Hepcidin synthesis causing increased iron absorption

Question 20

How does hereditary haemochromatosis present?

Answer 20

usually middle aged or later
iron overload >5g
non specific symptoms: weakness, fatigue, joint pains, impotence
long term: arthritis, cirrhosis, diabetes, cardiomyopathy

Question 21

What are the diagnostic features of hereditary haemochromatosis?

Answer 21

transferrin saturation >50%

serum ferritin >300g/l in men or >200g/l in women

Question 22

What is the treatment of hereditary haemochromatosis?

Answer 22

weekly venesection - want ferritin <20

screen first degree relatives

Question 23

What causes secondary iron overload?

Answer 23

massive ineffective eryhropoeisis - B thala major, sideroblastic anaemia
refractory hypoplastic anaemias - bone marrow doesnt work - myelodysplasia and red cell aphasia

Question 24

How is secondary iron overload treated?

Answer 24

iron chelating agents - desferrioxamine