Biochem - Bone Pain

Question 1

Supply of vit D

Answer 1

D3 (ergocalciferol)
D2 (cholecalciferol)

Requires UVB rays

Question 2

D2

Answer 2

Synthesised in our skin

Question 3

D3

Answer 3

Primarily derived from our diet

Question 4

Sources of vit D in our diet

Answer 4

Oily fish 
Meat 
Eggs 
Milk 
Fortified cereal

Question 5

Distribution of plasma Ca

Answer 5

50% protein bound (albumin)

50% ionised

Question 6

Regularatory functions of Ca

Answer 6

Neurotransmission 
Reproduction 
Hormone action 
Cellular growth 
Enzyme growth

Question 7

Hypocalcaemia

Answer 7

Albumin adjusted Ca < 2.2. mol/L

Question 8

Symptoms of hypocalcaemia

Answer 8

Paraethesia
Muscle spasm and tetany
Cardiac abnormalities
Coma

Question 9

Hypercalcaemia

Answer 9

Albumin adjusted Ca > 2.6 mol/L

Question 10

Symptoms of hypercalcaemia

Answer 10

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

Question 11

% absorption of Ca

Answer 11

15 - 50%

Question 12

What does the percentage of intestinal Ca absorption depend on

Answer 12

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

Question 13

Factors affecting intestinal Ca

Answer 13

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

Question 14

Sources of Ca

Answer 14

Dairy products

Cereals and cereal products

Question 15

What can Ca and vit D deficiency both cause

Answer 15

2’ hyperparathyroidism

Question 16

Causes of Ca deficiency

Answer 16

Low supply - low dietary intake

Low absorption

Question 17

Causes of vit D deficinecy

Answer 17

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

Question 18

Metabolism of vit D

Answer 18

D2, D3 –> 25OHD –> 1,25(OH)2D

Question 19

Where does the hydroxylation of vit D occur

Answer 19

Occurs in the liver

Question 20

Where does the hydroxylation of 25OHD occur

Answer 20

Kidney

Question 21

25OHD (calcidiol)

Answer 21

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

Question 22

Threshold of deficiency for plasma 25OHD

Answer 22

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

Question 23

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

Answer 23

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

Question 24

Spp pt groups at increased risk of low 25OHD

Answer 24

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

Question 25

Condns caused by vit D deficiency

Answer 25

Rickets and osteomalacia
Muscle weakness
Cardiomyopathy
Hypocalcaemic fits

Question 26

Processes affected by vit D deficiency

Answer 26

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

Question 27

Dx for rickets

Answer 27

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

Question 28

Bloods for rickets

Answer 28

25OHD
CaALB
boneALP

Question 29

Urine tests for rickets

Answer 29

Ca

P

Question 30

1,25(OH)2D (calcitriol)

Answer 30

Metabolically active form of vit D

Short half-life