Biochem - Bone Pain Flashcards Preview

MBBS - Year 1 > Biochem - Bone Pain > Flashcards

Flashcards in Biochem - Bone Pain Deck (30)
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1
Q

Supply of vit D

A

D3 (ergocalciferol)
D2 (cholecalciferol)

Requires UVB rays

2
Q

D2

A

Synthesised in our skin

3
Q

D3

A

Primarily derived from our diet

4
Q

Sources of vit D in our diet

A
Oily fish 
Meat 
Eggs 
Milk 
Fortified cereal
5
Q

Distribution of plasma Ca

A

50% protein bound (albumin)

50% ionised

6
Q

Regularatory functions of Ca

A
Neurotransmission 
Reproduction 
Hormone action 
Cellular growth 
Enzyme growth
7
Q

Hypocalcaemia

A

Albumin adjusted Ca < 2.2. mol/L

8
Q

Symptoms of hypocalcaemia

A

Paraethesia
Muscle spasm and tetany
Cardiac abnormalities
Coma

9
Q

Hypercalcaemia

A

Albumin adjusted Ca > 2.6 mol/L

10
Q

Symptoms of hypercalcaemia

A
Nausea 
Peptic ulcers 
Constipation 
Renal stones and failure 
Polyuria 
Soft tissue calcification 
Mental disturbance 
Depression
11
Q

% absorption of Ca

A

15 - 50%

12
Q

What does the percentage of intestinal Ca absorption depend on

A

Intake
Active absorptions
Life stage
Physiological state: growth, pregnancy, lactation

13
Q

Factors affecting intestinal Ca

A
Vit D status and active vit D
Age - postmenopausal decreases 0.21%/yr
Bioavailability of food 
GI disorders 
Phosphate and phytate binding
14
Q

Sources of Ca

A

Dairy products

Cereals and cereal products

15
Q

What can Ca and vit D deficiency both cause

A

2’ hyperparathyroidism

16
Q

Causes of Ca deficiency

A

Low supply - low dietary intake

Low absorption

17
Q

Causes of vit D deficinecy

A
Low sunshine exposure 
Low dietary supply 
Low absorption 
Obesity 
High loss and/ or utilisation
18
Q

Metabolism of vit D

A

D2, D3 –> 25OHD –> 1,25(OH)2D

19
Q

Where does the hydroxylation of vit D occur

A

Occurs in the liver

20
Q

Where does the hydroxylation of 25OHD occur

A

Kidney

21
Q

25OHD (calcidiol)

A

Conc reflects balance of vit D supply and expenditure
Integrated marker of vit D supply (skin, diet, reserves)
Long half life as principally circulating form of vit D

22
Q

Threshold of deficiency for plasma 25OHD

A

Defined as a level of plasma 25OHD above which rickets and osteomalacia are not seen
>25 mmol/L is deficient but 25-50 may be inadequate

23
Q

Of a general healthy pop., groups most at risk of low 25OHD are

A
Dark skinned individuals 
Concealing dress style 
Little UVB exposure 
Obesity 
Adolescents 
Frail elderly 
Exclusively breast-fed babies
24
Q

Spp pt groups at increased risk of low 25OHD

A
Renal disease 
GI disorders 
Coeliac disorders 
ICU pt 
Severe liver disease 
Cystic fibrosis 
TB
25
Q

Condns caused by vit D deficiency

A

Rickets and osteomalacia
Muscle weakness
Cardiomyopathy
Hypocalcaemic fits

26
Q

Processes affected by vit D deficiency

A

Chondrocyte function and apoptosis
Lack of calcification of GP cartilage
Lack of calcification of osteoid
Osteoblast, osteocyte and octeoclast function

27
Q

Dx for rickets

A

Clinical features, radiology
Medical and diet history
Biochem - blood and urin

28
Q

Bloods for rickets

A

25OHD
CaALB
boneALP

29
Q

Urine tests for rickets

A

Ca

P

30
Q

1,25(OH)2D (calcitriol)

A

Metabolically active form of vit D

Short half-life

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