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MEH > B12, Folate + Iron > Flashcards

B12, Folate + Iron Flashcards

(62 cards)

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1
Q

Where is folate synthesised in?

A

Bacteria + plants

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2
Q

Where is folate mainly absorbed from?

A

Duodenum
Jejunum

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3
Q

Outline the path of folate in the body

A
  • eaten
  • absorbed mainly from duodenum + jejunum
  • converted to tetrahydrofolate by intestinal cells
  • taken up by liver which acts as a store
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4
Q

Where is folate stored?
How long does it last?
How fast is it used up in anaemia?

A

Liver
3-4 months
Anaemia - 2 to 3 weeks

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5
Q

Causes of folate deficiency

A
  • Poor diet
  • Increased requirement - pregnancy, increased erythropoiesis
  • Disease of duodenum or jejunum e.g. Crohn’s disease, coeliac disease
  • Alcoholism
  • Liver disease or heart failure - urinary loss of folate
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6
Q

Signs + symptoms of folate deficiency

A
  • Those relating to anaemia - pallor, tiredness, breathless
  • reduced sense of taste
  • diarrhoea
  • numbness and tingling in feet and hands
  • muscle weakness
  • depression
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7
Q

What can be used to prevent neural tube defects in babies during pregnancy?

A

Folic acid before conception + during 1st 12 weeks of pregnancy

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8
Q

What benefit does folic acid have of taken during pregnancy?

A

Prevents neural tube defects

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9
Q

Uses of vitamin B12

A
  • cofactor for DNA synthesis
  • needed for normal erythropoiesis
  • normal function + development of CNS
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10
Q

Good sources of vitamin B12

A

Meat
Fish
Milk
Cheese
Eggs
Yeast extract

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11
Q

Outline vitamin B12 absorption

A
  • B12 binds to haptocorrin in stomach
  • haptocorrin B12 complex digested by pancreatic proteases > B12 released
  • B12 binds to intrinsic factor
  • IF-B12 complex enters enterocytes in terminal ileum via receptor-mediated endocytosis
  • binds to transcobalamin in blood + transported
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12
Q

Where is vit B12 stored?
How long does it last for?

A

Liver
3-6 years

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13
Q

Causes of vitamin B12 deficiency

A
  • Poor diet - vegan diet lacks B12
  • lack of intrinsic factor&raquo_space; pernicious anaemia
  • disease of ileum e.g. Crohn’s disease
  • lack of transcobalamin
  • chemical inactivation of B12
  • parasitic infection&raquo_space; can trap B12
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14
Q

Signs and symptoms of vitamin B12 deficiency

A
  • those relating to anaemia - pallor, fatigue etc.
  • glossitis
  • mouth ulcers
  • Paraesthesia
  • irritability
  • diarrhoea
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15
Q

What causes pernicious anaemia

A

Decreased or absent intrinsic factor&raquo_space; progressive exhaustion of B12 reserves

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16
Q

What does folate deficiency in pregnancy cause?

A

Neural tube defects

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17
Q

Effect of B12 deficiency on nervous system

A
  • Focal demyelination - B12 needed for myelin sheath production
  • Reversible peripheral neuropathy - most common
  • Subacute combined degeneration of cord - irreversible
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18
Q

What is subacute combined degeneration of the cord due to?

A

vit B12 deficiency

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19
Q

Symptoms of subacute combined degeneration of the cord

A
  • Gradual onset weakness + Paraesthesia in arms, legs + trunk which gets worse
  • Change in mental state
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20
Q

Link between B12 and folate

A
  • B12 is needed for stable methyltetrahydrofolate to be converted to tetrahydrofolate
  • lack of B12 prevents this + stops FH4 from being used in synthesis of thymidine for DNA synthesis
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21
Q

Why do B12 + folate deficiencies cause megaloblastic anaemia?

A
  • cause a thymidine deficiency
  • uracil is incorporated into DNA instead
  • DNA repair enzymes detect the errors + constantly repair by excision
  • results in nucleus not fully maturing as cytoplasm matures at normal rate > megaloblast > larger RBCs
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22
Q

Megaloblastic features in blood film

A

Tear drop RBCs
Anisopoikilocytosis - variance in size + shape
Ovalocytes
Hypersegmented neutrophils - >6 lobes more
Macrocytic RBCs

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23
Q

Treatment of folate deficiency

A

Oral folic acid

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24
Q

Treatment of vitamin B12 deficiency

A
  • Due to pernicious anaemia - IM hydroxocobalamin (NOT ORAL - due to no intrinsic factor)
  • Other causes - oral cyanocobalamine
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25
How does the body excrete iron?
No mechanism for excreting iron
26
How is free iron toxic to cells?
Contributes to formation of free radicals
27
Two types of iron and their charges What type does the body like + not like?
**Ferrous iron 2+** - Likes **Ferric iron 3+** - Ick’ doesnt like
28
What does two things does dietary iron consist of?
**Haem iron** - Fe2+ **Non haem iron** - mixture of 2+ and 3+
29
What form of iron can be absorbed?
Ferrous Fe2+
30
Where is iron absorbed?
Duodenum Jejunum
31
Outline dietary absorption of iron
*reductase* - Fe3+ > Fe2+ - **DMT1** takes up Fe2+ into enterocyte - stored as **ferritin** in form of Fe3+ - **ferroportin** transports Fe2+ into bloodstream *hephaestin* Fe2+ > Fe3+ - Fe3+ binds to **transferrin** + transported around body
32
What has a negative influence on absorbing iron from food? Why?
- **Tannins** - in tea - **Phytates** *e.g chapattis + pulses* - **Fibre** - **Antacids** - Can bind non haem iron in intestine > reduces absorption
33
What has a positive influence on absorbing iron from food?
Vitamin C + citrate
34
What is deficient in pernicious anaemia?
Intrinsic factor
35
What cells secrete intrinsic factor
Parietal cells
36
Action of hepcidin
Inhibits action of ferroportin Fe2+ gets trapped in enterocyte
37
How is iron stored?
Soluble ferritin Fe3+ Insoluble haemosiderin
38
Outline cellular uptake of iron
- **Fe3+ bound transferrin** bind to transferrin receptor - taken up by **receptor mediated endocytosis** at target cell - Fe3+ > Fe2+ - Fe2+ transported to cytosol via **DMT1** - Fe2+ **stored as ferritin**, **exported by ferroportin** or taken up by mitochondria for **cytochrome enzymes**
39
Control mechanisms to regulate iron absorption
- regulation of transporters - regulation of receptors - hepcidin
40
Where is hepcidin released from? Stimulated by Inhibited by
Liver S - Increase in iron overload I - high erythropoietic activity
41
Causes of iron deficiency
Poor diet Malabsorption of iron Bleeding Increased requirement Anaemia of chronic disease
42
Signs and symptoms of iron deficiency
- Fatigue - Pallor - Pica - unusual craving for non-nutritive substances e.g. ice, dirt - cold peripheries - epithelial changes - koilonychia - angular cheilitis
43
Iron deficiency in blood film
Microcytic Hypochromic Anisopoikilocytosis Sometimes pencil + target cells
44
How do you diagnose iron deficiency?
- **Reduced plasma ferritin** >> definitely indicates iron deficiency - Normal or increases does not exclude iron deficiency as it can be increased due to other reasons
45
Treatment of iron deficiency
Dietary advice Oral iron supplements - **ferrous sulphate** IM iron injection IV iron
46
FBC results in iron deficiency
Low MCV Low ferretin, iron Raised TIBC Low CHr - reticulocyte haemoglobin content
47
What can excess iron cause? What can cause excess iron?
- Deposited in organs as haemosiderin - Promotes free radicals formation . - transfusion associated haemosiderosis - hereditary haemochromostosis
48
What is hereditary haemochromtosis?
- Autosomal recessive disease casued by mutation in HFE gene - Normally promotes hepcidin + reduces transferrin receptor affinity - Mutation in HFE gene doesnt allow this to happen - causing too much iron to enter cells > accumulates in end organs > damage
49
Treatment of hereditary haemochromatosis
Venesection
50
What free radicals are made by excess iron? What are is this reaction called?
Hydroxyl + hydroperoyl Fenton reaction
51
Reasons for increased ferritin levels
Cancer Infection Inflammation Liver disease Alcoholism
52
Role of folate
- involved in synthesis of nucleotide bases needed for DNA + RNA synthesis - provide carbons for other reactions
53
What is B12 produced by?
Bacteria
54
What needs to be considered when treating B12 deficiency in patients with pernicious anaemia?
- *hydroxycobalamine* - **drug NOT given orally**: no intrinsic factor so B12 wouldn’t be absorbed - **hypokalaemia**: due to increased K+ requirement as erythropoiesis increases
55
Dietary sources of haem iron
Liver Kidney Tuna Salmon Chicken Beef Pork
56
Dietary sources of non-haem iron
Potatoes Rice Oats Beans Fortified cereals
57
What is used to test for functional iron deficiency?
CHr (reticulocyte haemoglobin content)
58
What is transfusion associated haemosiderosis?
- condition that occur when repeated blood transfusions are given - causes iron levels to quickly build up
59
What can be used to help the effects of transfusion associated haemosiderosis?
**Iron chelating agents** Delay NOT prevention
60
Risk groups for iron deficiency anaemia
- Menorrhagic women - Infants being weaned off breast to solid foods - women of child bearing age - geriatric age group
61
What is given as an oral replacement for iron?
Ferrous sulphate
62
What two conditions can cause excess iron?
Transfusion associated haemosiderosis Hereditary haemochromostosis

MEH (23 decks)

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