Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Haematology > Iron in Health and Disease > Flashcards

Iron in Health and Disease Flashcards

1
Q

What are some of the functions of iron?

A

Oxygen transport = reversible oxygen binding by Hb

Electron transport

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What are some molecules that contain iron?

A

Haemoglobin, myoglobin and enzymes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What are some of the issues with iron?

A

Can produce free radicals and cause oxidative stress

No mechanism for its excretion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Where is the majority of body iron found?

A

In haem = Fe2+sits in porphyrin ring

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Where does iron absorption mainly occur?

A

In the duodenum = uptake into duodenal mucosal cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What influences iron absorption?

A

Dietary factors

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What are some dietary chemicals that influence iron absorption?

A

Enhanced by ascorbic acid (reduces iron to Fe2+) and alcohol

Inhibited by tannins, phylates and calcium

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What are the different mechanisms of iron absorption?

A

Duodenal cytochrome B, DMT-1 and ferroportin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

How does duodenal cytochrome B absorb iron?

A

Found in lumenal surface = reduces ferric iron (Fe3+) to ferrous form (Fe2+)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

How does DMT-1 absorb iron?

A

Transports ferrous iron into duodenal enterocytes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

How does ferroportin absorb iron?

A

Facilitates iron export from enterocyte where it is passed on to transferrin for transport elsewhere

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is hepcidin?

A

Major negative regulator of iron uptake = levels decrease in iron deficiency

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Where is hepcidin produced?

A

Produced in liver in response to increased iron load and inflammation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is the action of hepcidin?

A

Binds to ferroportin and causes its degradation = iron trapped in duodenal cells and macrophages

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

How is iron status assessed?

A

Functional iron = Hb concentration
Transport iron = % saturation of transferrin
Storage iron = serum ferritin, tissue biopsy (rarely used)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is transferrin?

A

Protein with two binding sites for iron = transports iron from donor tissues to those expressing transferrin receptors

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What area of the body is especially rich in transferrin receptors?

A

Erythroid marrow

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What does saturation of transferrin measure?

A

Iron supply = serum iron/total iron binding capacity x 100

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What does % saturation of transferrin reflect?

A

Proportion of diferric transferrin = has high affinity for cellular transferrin receptors

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What do the different types of transferrin represent?

A

Holotransferrin represents bound

Apotransferrin represents unbound

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

How do transferrin saturation vary in different iron states?

A

In normal levels, saturation is 20-50%

Elevated saturation in iron overload

22
Q

What is ferritin?

A

Spherical intracellular protein = stores up to 4000 ferric ions

23
Q

What does serum ferritin reflect?

A

Tiny amount of serum ferritin reflects intracellular ferritin synthesis = indirect measure of storage iron

24
Q

What is the additional function of ferritin?

A

Acts as an acute phase protein

25
Q

What causes ferritin levels to rise?

A

Iron overload, sepsis, inflammation, malignancy

26
Q

What are examples of disorders of iron metabolism?

A

Iron deficiency, iron malutilisation (anaemia of chronic disease), iron overload

27
Q

What are the consequences of negative iron balance?

A

Exhaustion of iron stores
Iron deficient erythropoiesis = falling rec cell MCV
Microcytic anaemia
Epithelial changes = skin, koilonychia, angular stomatitis

28
Q

Is iron deficiency anaemia a diagnosis?

A

No = symptom not a diagnosis, iron replacement therapy will mask symptoms but won’t treat underlying problem

29
Q

What causes increased ferritin synthesis in anaemia of chronic disease?

A

Increased transcription of ferritin in mRNA stimulated by inflammatory cytokines

30
Q

What effect does anaemia of chronic disease have on iron release?

A

Increased plasma hepcidin blocks ferroportin-mediated release of iron

31
Q

What is the end result of anaemia of chronic disease?

A

Results in impaired iron supply to marrow erythroblasts and eventually hypochromatic red cells

32
Q

Why does inflammatory macrophage iron block occur in anaemia of chronic disease?

A

Protective mechanism = reduces iron supply to pathogens

33
Q

What are some causes of iron overload?

A 
Primary = hereditary haemochromatosis
Secondary = transfusional, iron loading anaemias
34
Q

What occurs in primary iron overload?

A

Long term excess iron absorption with parenchymal rather than macrophage iron loading

35
Q

What causes the most common form of hereditary haemochromatosis?

A

Mutation in HFE gene

36
Q

What occurs in hereditary haemochromatosis?

A

Decreases synthesis of hepcidin = increased iron absorption resulting in gradual iron accumulation with risk of end organ damage

37
Q

When does hereditary haemochromatosis present?

A

In middle age or older when iron overload >5g = may be asymptomatic until end-organ damage has occurred

38
Q

What are the features of hereditary haemochromatosis?

A

Weakness/fatigue, arthritis, cirrhosis, joint pains, impotence, diabetes, cardiomyopathy

39
Q

What are some features of mutations in HFE causing hereditary haemochromatosis?

A

Accounts for 95% of cases
H63D mutation most common followed by C282Y
Patients usually C282Y homozygotes
Shows incomplete penetrance

40
Q

How is hereditary haemochromatosis diagnosed?

A

Transferrin saturation >50% on repeated fasted test
Serum ferritin >300ug/l in men or >200ug/l in women
Liver biopsy = rarely needed, non-invasive techniques like Fibroscan can assess cirrhosis

41
Q

How is hereditary haemochromatosis treated?

A

Weekly venesection = 400-500ml, 200-250mg iron
Initial aim to exhaust iron stores = ferritin <20ug/l
Thereafter keep ferritin <50ug/l

42
Q

What patients are screened for hereditary haemochromatosis?

A

All first degree relatives of patients (esp siblings)

Wait until children are adults

43
Q

How is hereditary haemochromatosis screened for?

A

HFE genotype and iron status = ferritin and transferrin status

44
Q

What are the causes of iron loading anaemias?

A

Repeated red cell transfusions, excessive iron absorption related to overactive erythropoiesis

45
Q

What are some disorders that cause iron loading anaemias?

A

Massive ineffective erythropoiesis = thalassaemias, sideroblastic anaemias
Refractory hypoplastic anaemias = red cell aplasia, myelodysplasia

46
Q

How much iron does each unit of blood given in a transfusion contain?

A

About 250mg of iron

47
Q

How often do patients with thalassaemia require transfusion?

A

Every 2-3 weeks lifelong

48
Q

What organs can be damaged by iron loading?

A

Liver, heart and endocrine glands

49
Q

What is the definition of iron loading?

A

Iron >5g or liver >15mg/g dry weight

50
Q

How are iron loading anaemias treated?

A

Venesection = not option in already anaemic patients

Iron chelating agents = desferrioxamine (SC or IV), oral deferiprone or deferasirax

Haematology (24 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions