haemoglobin 8: iron deficiency

Question 1

what are some examples of iron containing proteins?

Answer 1

haemoglobin, myoglobin, catalase, cytochrome P450, cytochrome a&b&c, succinate dehydrogenase, ribonucleotide reductase

Question 2

what is the structure of haem?

Answer 2

protoporphyrin ring in the middle with a central Fe that binds to oxygen

Question 3

why do we need dietary intake of iron?

Answer 3

although most iron is recycled some is lost from desqamated cells of skin & gut & menstruation

Question 4

how much iron do we need each day?

Answer 4

men = 1mg, women = 2mg

Question 5

what food sources provide iron?

Answer 5

meat & fish (good as iron already in haem)
vegetables
whole grain cereal

Question 6

what form of iron can we absorb?

Answer 6

Fe2+ (cannot absorb ferric Fe3+)

Question 7

what factors affect iron absorption?

Answer 7

• diet (eg consumption of haem iron / ferrous v ferric)
• intestine (eg acidity in duodenum)
• systemic (eg anaemia/hypoxia, pregnancy increases iron absorption)

Question 8

how does iron enter plasma from duodenal cells?

Answer 8

via ferroportin

Question 9

what regulates levels of ferroportin?

Answer 9

hepcidin (dependent on levels of iron)

Question 10

what happens when hepcidin levels are high?

Answer 10

hepcidin high -> binds to ferroportin -> ferroportin cannot transport iron

Question 11

what happens when iron is absorbed into plasma?

Answer 11

binds to transferrin (carrier protein)

Question 12

what effect does anaemia have on RBC production?

Answer 12

anaemia -> tissue hypoxia -> increase in erythropoietin -> increase in red blood cell production - red cell precursors survive longer and grow + differentiate

Question 13

what is ACD?

Answer 13

anaemia of chronic disease - anaemia in patients who are unwell

Question 14

what are the laboratory signs of being ill?

Answer 14

• high c-reactive protein
• high erythrocyte sedimentation rate
• acute phase response -> increase in ferritin / FVIII / fibrinogen / immunoglobulins

Question 15

what are some associated conditions of ACD?

Answer 15

• chronic infection eg TB, HIV,
• chronic inflammation eg RhA/SLE, malignancy,
• miscellaneous eg cardiac failure

Question 16

what do cytokines do in relation to iron in the system?

Answer 16

prevent iron utilisation by:

• blocking usual flow of iron from duodenum to red cells
• stopping increase in erythropoietin
• increasing production of ferritin

Question 17

what effects do cytokines therefore have?

Answer 17

• reduced production of red cells
• increased death of red cells
• less availability of iron

Question 18

what are the causes of iron deficiency?

Answer 18

• bleeding (eg menstrual/GI),
• increased use (eg growth, pregnancy)
• dietary deficiency (eg vegetarian)
• malabsorption (eg coeliac)

Question 19

when would you carry out a full GI investigation?

Answer 19

if good diet and no coeliac antibodies:

• male
• post-menopausal women
• women with light periods

Question 20

what is a full GI investigation?

Answer 20

upper GI endoscopy (oesophagus, stomach, duodenum), colonoscopy, duodenal biopsy & if nothing found -> small bowel meal and follow through

Question 21

what laboratory parameters can be measured to test for anaemia?

Answer 21

• MCV
• serum iron
• ferritin
• transferrin (=TIBC), transferrin saturation

Question 22

what are the 3 common causes of low MCV?

Answer 22

1. iron deficiency
2. thalassaemia trait
3. ACD (MCV could be low or normal)

Question 23

how can ferritin levels distinguish between iron deficiency & ACD?

Answer 23

low in iron deficiency, high in ACD (ferritin is an acute phase protein)

Question 24

how can transferrin levels distinguish between iron deficiency & ACD?

Answer 24

high in iron deficiency, normal/low in ACD

Question 25

how can transferrin saturation distinguish between iron deficiency & ACD?

Answer 25

low in iron deficiency, normal in ACD

Question 26

``` iron deficiency: Hb: MCV: Serum iron: Ferritin: Transferrin: Transferrin saturation: ```

Answer 26

``` Hb: LOW MCV: LOW Serum iron: LOW Ferritin: LOW Transferrin: HIGH Transferrin saturation: LOW ```

Question 27

``` ACD: Hb: MCV: Serum iron: Ferritin: Transferrin: Transferrin saturation: ```

Answer 27

``` Hb: LOW MCV: LOW/NORMAL Serum iron: LOW Ferritin: HIGH/NORMAL Transferrin: NORMAL/LOW Transferrin saturation: NORMAL ```

Question 28

``` Thalassaemia trait: Hb: MCV: Serum iron: Ferritin: Transferrin: Transferrin saturation: ```

Answer 28

``` Hb: LOW MCV: LOW Serum iron: NORMAL Ferritin: NORMAL Transferrin: NORMAL Transferrin saturation: NORMAL ```

Question 29

what are the clinical features of iron deficiency?

Answer 29

- fatigue - weakness - pale skin - lightheadedness - shortness of breath