Iron in health and disease

Question 1

What are the functions of iron?

Answer 1

oxygen transport; electron transport

Question 2

Why is iron dangerous?

Answer 2

chemical reactivity can cause oxidative stress

Question 3

What transporter is responsible for iron absorption in the duodenum int othe enterocyte?

Answer 3

divalent metal transporter-1

Question 4

What facilities iron export from the enterocyte?

Answer 4

ferroportin

Question 5

What is responsibel for down-regulation of ferroportin?

Answer 5

hepcidin

Question 6

What are the intraluminal factors regulating the absorption of iron?

Answer 6

solubility of inorganic iron; haem iron is easier to absorb; reuction of ferric to ferrous iron

Question 7

What are the mucosal factors invovled in iron absoprtion regulation?

Answer 7

expression of iron transporters

Question 8

What is hepcidin produced in reposne to?

Answer 8

in liver to iron load and inflammation

Question 9

What is the result of hepcidin?

Answer 9

iron trapped in duodenal cells and macrophages

Question 10

How is functional iron assessed?

Answer 10

haemoglobin concentration

Question 11

How is iron supply to tissues assessed?

Answer 11

% saturation of transferrin with iron

Question 12

What tissue is especcialy rich in transferrin receptors?

Answer 12

erythroid marrow

Question 13

How many binding sites does each transferrin protein have for iron?

Answer 13

2

Question 14

What is holotranserrin?

Answer 14

iron bound to transferrin

Question 15

What is apotransferrin?

Answer 15

unbound transferrin

Question 16

How is storage iron assessed?

Answer 16

serum ferritin or tissue biopsy

Question 17

what is ferritin?

Answer 17

spherical intracellular protein

Question 18

How much iron can ferritin store?

Answer 18

upto 4000 ferric (3+) ions

Question 19

What does serum ferritin reflect?

Answer 19

intracellular ferritin synthesis

Question 20

Aside from iron storage, what is ferritin involved in ?

Answer 20

acute phase protein- infection; malignancy

Question 21

What are hte broad categories of disorders of iron metabolism?

Answer 21

iron deficiency; iron malutilisation eg anaemia of chronic disease; iron overload

Question 22

What are the consequences of negative iron balance?

Answer 22

exhaustion of iron stores; iron deficiency erythropoieis; microcytic anaemia; epithelial changes

Question 23

What epithelial changes are seen with iron deficiency?

Answer 23

skin; koilonychia; angular stomatitis

Question 24

What does a hypochromic microcytic anemai indiciate?

Answer 24

deficiency haemoglobin synthesis- eg either haem or globin deficinecy

Question 25

What are hte causes of iron deficiency?

Answer 25

insufficient intake; bleeding; malabsorption

Question 26

What are the main causes of chronic blood loss?

Answer 26

menorrhagia; GI; haematuria

Question 27

How much GI blood loss can occur per day without any signs of symptoms?

Answer 27

8-10mls (4-5mg of iron)

Question 28

What is the maximum daily dietary iron absoprtion ?

Answer 28

4-5mg

Question 29

What happens in anaemia of chronic disease?

Answer 29

increased transcription of ferrritin mRNA stimulated by inflammatory cytokines; increased plasma hepcidin blocks ferroportin-mediated release of iron; imparied iron supply to marrow erythroblasts

Question 30

What is a primary cause of iron overload?

Answer 30

hereditary haemochromatosis

Question 31

What are secondary causes of iron overload?

Answer 31

transfusional; iron loading anaemia

Question 32

What is seen with priamry iron overload?

Answer 32

long-term excess iron absorption with parenchymal rather than macrophage iron loading

Question 33

What is the most commonest form of hereditary haemochromatosis?

Answer 33

mutations in HFE- decreased synthessi of hepcidin

Question 34

Waht are the clinical features of hereditary haemochromatosis?

Answer 34

weakness/fatigue; joint pain;s impotence; arthritis; cirrhosis; diabetess; cardiomyopathy

Question 35

How is the diagnosis of hereditary haemochromatosis made?

Answer 35

transferrin sat>50%; serum ferritin >300ug/L men or >200ug/l in women

Question 36

What are the causes of iron-loading anaemias?

Answer 36

repeated transfusions; excessive iron absorption due to over-active eryhropoiesis

Question 37

What are the disorders associatedwtih iron-loading anaemia?

Answer 37

massive ineffective erythropoieisis: thalassaemia syndromes; sideroblastic anemias; refractory hypoplastic anaemias: red cell aplasia; myelodysplasia

Question 38

How much iron does one unit of blood contain?

Answer 38

250mg

Question 39

What ate the iron chelating agents?

Answer 39

desferrioxamine; deferiprone; deferasirox