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Year 2 Loco > 4. Metabolic bone conditions (Robson) > Flashcards

4. Metabolic bone conditions (Robson) Flashcards

1
Q

What is used to diagnose metabolic bone conditions?

A

Serum blood tests

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2
Q

What will serum blood test results show in osteoporosis?

A

The blood test results will generally show as normal

MAY be slightly low level of calcium and vitamin D

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3
Q

What is osteoporosis?

A

Reduced bone density occurring from a loss of tissue due to calcium or vitamin D deficiency

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4
Q

Does osteoporosis affect men or women more and why?

A

Affects women more - women start off with a lower bone mass in life (and then are effected by the menopause due to loss of oestrogen protection)

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5
Q

What is the key investigation used to assess osteoporosis and reduced bone mass?

A

DEXA scan - used to measure the bone mass - gives you a T or Z score

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6
Q

What does the T score from a DEXA scan take into account?

A

Number of SDs from a young individual of the same same sex and same ethnicity

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7
Q

What does the Z score from a DEXA scan take into account?

A

Number of SDs from an individual of the SAME AGE, same sex and same ethnicity

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8
Q

How does the Z score differ from the T score from a DEXA scan?

A

Z score - takes into account the age of the individual

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9
Q

Where is a DEXA scan used?

A

Scan where there is lots of trabeculae bone - top of the femur and at the vertebral bodies (especially lumbar vertebrae

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10
Q

What DEXA T score indicates osteoporosis?

A

T score below 2.5

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11
Q

What is osteopenia and what is this on the DEXA T score?

A

Reduced bone density but not as severe as osteoporosis

T score between -1 and -2.5

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12
Q

What is a fragility fracture?

A

A fracture that occurs where someone with a full bone density would not experience a fracture

E.g. a fracture from a trip and the hip bends slightly rather than an actual fall

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13
Q

What is indicated by a fragility fracture?

A

This indicates that the bones are becoming fragile and are breaking more easily than they should - should send anyone with a fragility fracture for a DEXA scan

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14
Q

What is the prevalence of osteoporosis?

A

2% at 50 years old

>25% at 80 years old

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15
Q

Why is trabecular bone more prone to osteoporosis?

A

Has a greater surface area

This type of bone is in locations that has to respond to new stresses and increased levels of mechanical stress

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16
Q

What is the mechanism of osteoporosis?

A

There is an increase in the rate of resorption of the bone which is not matched by the rate of bone formation - there is less bone

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17
Q

Describe the activity of the osteoclasts and osteoblasts in osteoporosis

A

Osteoblasts are not as active as the osteoclasts

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18
Q

Where are bone biopsies for osteoporosis taken and why?

A

Tend to be taken across the iliac crest - this shows cortical bone and trabecular bone and also bone marrow

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19
Q

What does osteoporotic bone look like in a biopsy?

A

The cortical bone will appear normal - there will be a loss of trabeculae bone centrally

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20
Q

What is the treatment for osteoporosis?

A

Non-pharmacological treatment: calcium and vitamin D supplements and 30 minutes physical activity at least three times a week

HRT - oestrogen replacement in peri-menopausal women for at least five years

Bisphosphonates

Antibodies

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21
Q

What level of calcium and vitamin D supplement should be provided to osteoporotic patients?

A

Calcium - 1500mg/day

Vitamin D - 800IU/day

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22
Q

What are bisphosphonates and what are their mechanism of action?

A

Group of drugs that are absorbed into bone when taken - become incorporated into the bone
Osteoclasts then come to the bone and take the bisphosphonates up along with the bone resorption
The bisphosphonate is taken up into the osteoclast and this promotes their apoptosis - osteoclast activity is inhibited

May also act to modulate signalling to osteoblasts and decrease their production of RANKL - this reduces the signal to osteoclasts and so they cease to proliferate and differentiate

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23
Q

What is the efficacy of bisphosphonates?

A

Reduce the risk of fragility fractures by 50%

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24
Q

What is the adverse effect of bisphosphonate usage?

A

Some osteoclasts do not clamp down on the bone that has taken up the bisphosphonate - results in the development of giant osteoclasts free floating in the bone marrow - the osteoclasts do not carry out their role of remodelling and there is necrosis of the bone due to death of osteocytes

SO: major complication is osteonecrosis

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25
Q

How can osteonecrosis be prevented?

A

Intermittent use of bisphosphonates - take the patient off of these for e.g. six months at a time - gives osteoclasts time to remodel the bone

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26
Q

What is teriparatide and how is it used to treat osteoporosis?

A

Short term PTH
PTH activates osteoblasts in the short term and osteoclasts in the long term

SO short term PTH ensures that osteoblasts are still activated by osteoclasts are not

27
Q

What is denosumab?

A

Relatively new - antibody treatment

Binds to RANKL to prevent it from getting to and activating the osteoclasts

28
Q

What is osteomalacia?

A

AKA. Rickets

Insufficient calcium and phosphate to mineralise the new bone osteoid due to deficient vitamin D
Condition of the woven bone

SO - LACK OF BONE MINERALISATION

29
Q

How does osteomalacia show on a serum blood test?

A 
Low calcium 
Low phosphate 
High ATP
High PTH
Low vitamin D
30
Q

How do osteomalacia and osteoporosis differ from each other?

A

Osteoporosis - decreased total bone mass but normal ratio of the matrix to mineral i.e. matrix to bone

Osteomalacia - decreased ratio of mineral to matrix i.e. higher level of matrix compared to relative levels of bone

31
Q

What is the most common presentation of osteomalacia?

A

Bow legs - genu varum

32
Q

Is osteomalacia more damaging in adults or children and why?

A

More damaging in children - their epiphyseal growth plates are still open and these widen lengthways (top to bottom) - more deforming

33
Q

What are pseudofractures in osteomalacia?

A

In adults
Where there is new bone formation e.g. bone remodelling - mineralisation does not occur - psuedofractures - regions of unmineralised bone

34
Q

How does osteomalacia appear in a bone biopsy?

A

Normal bone - has less than 20% unmineralised bone

Osteomalacia - see wide streams of unmineralised osteoid casing the mineralised osteoid

35
Q

What is the treatment for osteomalacia?

A

Vitamin D supplements - may be required for the rest of their life
Dietary increase in calcium
Increased sun or UV exposure

36
Q

Give five food groups high in calcium

A 
Milk 
Bread
Beans and pulses
Dried fruit
Green leafy veg
37
Q

How much sun exposure should an individual have to get sufficient levels of vitamin D?

A

15 minutes of sun on the hands and face 2-3 times a week

38
Q

What is Paget’s disease?

A

Condition where the normal cycle of bone renewal and repair is disrupted

39
Q

What are the three stages of Paget’s disease?

Describe these

A

Initial phase - increased rate of bone resorption - large number of giant osteoclasts

Compensatory/proliferative phase - increased bone formation - accelerated deposition in disorganised manner (making woven bone very quickly in an attempt to compensate for the increased resorption

Burnt out phase - bone hypercellularity and hyper-vascular bone marrow

40
Q

What are the bones commonly affected in Paget’s disease?

A 
Pelvis 
Femur 
Vertebrae 
Skull 
Tibia
41
Q

Does Paget’s disease tend to be unilateral or bilateral?

A

Unilateral

42
Q

What is the relation of osteosarcoma and Paget’s disease?

A

Osteosarcoma is a rare complication of Paget’s disease - often occurs in the young

Occurs due to the giant osteoclasts and rapid proliferation

43
Q

What is the treatment for Paget’s disease?

A

Bisphosphonates - work directly on the osteoclasts to slow bone resorption
Calcium and vitamin D supplements
Pain management
Surgery

44
Q

What is slerostosis?

A

This is a condition where there is an absence or reduced production of sclerostin

45
Q

What is the rationale for providing calcium supplements to patients with osteoporosis?

A

Calcium supplements will bring the serum calcium levels to the range in which they are required
This will cause PTH levels to fall (due to release of calcitonin)
PTH stimulates activity of osteoclasts and so:
PTH levels fall - reduced activity of osteoclasts and reduced bone resorption - decreases onset of osteoporosis

46
Q

What is the rationale for providing vitamin D supplementation to patients with osteoporosis?

A

1,25-hydroxyvitamin D (active form) increases calcium absorption in the gut

This will result in falling PTH levels due to release of calcitonin - reduced osteclast activity

47
Q

Function of bisphosphonates x2

A

Inhibition of osteoclast activity

Inhibition of RANKL production from osteoclasts

48
Q

Bisphonates have action on what cell type?

A

Osteoclasts

49
Q

PTH - short term action is on which cells?

A

Osteoblasts

50
Q

PTH - long term action is on which cells?

A

Osteoclasts

51
Q

Teriparatide has action on which cells

A

Teriparatide - short term PTH

Acts of osteoblasts

52
Q

Cause of osteomalacia?

A

Insufficient calcium and phosphate levels

53
Q

Technical term for bow legs is?

A

Genu Varum

54
Q

In normal bone - what is the percentage of unmineralised osteoid?

A

<20%

55
Q

In osteomalacia, what is the percentage of unmineralised none?

A

> 20%

56
Q

Three stages of Paget’s disease are?

A

Initial
Compensatory/proliferative
Burn out

57
Q

Main feature of initial stage in Paget’s disease is?

A

Increased bone resorption via giant osteoclasts

58
Q

Main feature in compensatory/proliferative stage of Paget’s disease is? x2

A

Increased bone formation

Deposition of bone in disorganised manner

59
Q

Main feature of burnt out phase in Paget’s disease is? x3

A

Sclerosis
Cement lines - prominent
Bone marrow replaced with fibrovascular connective tissue

60
Q

What is Van Buchem syndrome?

A

Reduced production of sclerostin

61
Q

Sclerostin is secreted from which cells?

A

Osteocytes

62
Q

Consequence of Van Buchem syndrome is?

A

Hyperactivity of osteoblasts

63
Q

Inheritance of Van Buchem syndrome is?

A

Autosomal recessive

Year 2 Loco (31 decks)

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