Metabolic bone conditions Flashcards

discuss the pathoogenesis and management for the folowing: -osteoporosis -osteosclerosis -osteomalacia -Paget's

1
Q

Which 5 factors measured in a blood test differentiate between metabolic bone conditions?

A
  1. Ca
  2. PO4
  3. Alkaline phosphtase
  4. PTH
  5. active form vit D3 =1,25(OH)2 vit D
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2
Q

what is osteoporosis?

A

loss of bone mass - bone reabsorption > formation

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3
Q

what age does bone mass loss occur?

A

> 40 yrs loss 0.7% bone mass per year

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4
Q

In females what event speeds up bone loss and why?

A

MENOPAUSE (increases bone loss 2-9% per year) - loss of oestrogen - omj increase bone reabsorption + decreases Ca absorption from gut

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5
Q

Why is osteoporosis less common in men?

A

Men have

  1. more MUSCLE- more stress on skeleton - increases bone mass
  2. more TESTOSTERONE - anabolic steroid - increases muscle + bone mass

THEREFORE MEN HAVE MORE BONE TO BEGIN WITH THAN WOMEN

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6
Q

What age does bone mineral density peak?

A

25-27yrs

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7
Q

What is the peak bone mass in both males and females?

A

males = 1500g

females =1000g

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8
Q

What does bone mass measure?

A

the total mass of claicum in the skeleton in grams

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9
Q

How is bone mineral density measured?

A

T or Z score

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10
Q

What is a T score?

A

no. of SD from young (30yr) + same sex + ethnicity

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11
Q

What is a Z score?

A

no of SD from old+ same sex + ethnicity

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12
Q

Which is more commonly used + why?

A

T score - more data been measured for this

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13
Q

What equipment is used to measure T/Z score?

A

DEX scan

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14
Q

Interpretation of T score for normal/osteopenia/osteoporosis

A
  • normal = +/- 1 SD

- osteopenia = -1 2.5 SD

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15
Q

What type of bone is most suspectible to osteoporosis and why?

A

trabecular bone -

  1. greater S.A of sketelon
  2. finer collagen framework
  3. in areas suspectible to stress
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16
Q

What 2 areas of the body are commonly affected in osteoporosis + why?

A

vertebral bodies + femur neck - high proportion of trabeculae bone

17
Q

What are the 2 changes visible in osteoporotic bone?

A
  1. thinner cortices
    2.thinner trabeculae
    HOWEVER NORMAL OSTEOID - bone matrix :mineral not affected
18
Q

What is the 1st stage of osteoporosis treatment?

A

non pharmacological treatment

  1. Ca supplement = 1500mg/day
  2. Vitamin D = 800 IU/day
  3. exercise >30 mins,3 times a week =increase muscle mass - increase bone mass
19
Q

What is the 1st stage of osteoporosis treatement in menopauasal women?

A

HRT for at least 5 years

20
Q

What is raloxifene?

A

SERM - selective oestrogen receptor modulator - only affects oestrogen receptor in bone NOT uterus + breast - avoids uterine + breast cancer from overproduction of oestrogen

21
Q

Which pharmological treatment is most popular for osteoporosis?

A

Bisphosphonates -ending = ‘ate’ - alendronate + resdronate

22
Q

Why is the bisphosphonate ETIDRONATE only used as a last resort treatment option?

A

reduces osteoclast activity BUT ALSO bone calcification - osteomalacia

23
Q

Action of bisphosphonates

A

reduces osteoclastic activity- prevents bone resorption- stronger bone
reduces risk of fracture by 50%

24
Q

Complication of bisphosphonates

A

osteonecrosis of jaw + atypical fractures

25
Q

2 future treatments for osteoporosis

A

TERIPARATIDE - intermittent exposure to PTH- act. osteoblasts>osteoclasts
DENOSUMAB - subcutaneous injection , twice a year - inhibits osteoclasts

26
Q

What deficiency causes osteomalacia (rickets)?

A

vitamin D + calcium deficiency

27
Q

What is the consequence of vit D on bone?

A
  • insufficient Ca + PO4 to mineralise new bone osteoid

- bone becomes softer- bend/fracture

28
Q

Why is rickets more severe in children?

A

-epiphyseal growth plates are still open - more deforming - BOW LEGS

29
Q

Presentation of rickets in adults

A
  • psuedofractures

- areas of unmineralised bone at locations of high bone turnover

30
Q

In normal bone how much of the osteoid is unmineralised?

A

<20%

31
Q

What feature would be seen in a bone autopsy for osteomalacia?

A

high % of UNmineralised osteoid (up in 100% in severe cases)

32
Q

Treatment for osteomalacia

A

AIM = treat vit D + calcium deficiency

  • vit D supplements
  • increase dietary Ca intake
  • increase sun /U exposure (sunbed)
33
Q

What is another name for Paget’s disease?

A

osteitis deformans

34
Q

Describe the process bone resorption

A

osteoclasts break down bone - release minerals to blood (eg Ca)

35
Q

3 stages of Paget’s

A

1 INCREASED RATE OF BONE RESORPTION (hyperactive osteoclasts)

  1. compensatory phase -increase bone formation (hyperactive osteoblast- fill lacunae created by osteoclast overactivity - deposition woven bone in disorganised manner)
  2. BURNT OUT PHASE - both osteoclasts+ osteoblasts worn out - leaves DENSE Pagetic bone
36
Q

Key presentation of Paget’s

A

UNILATERAL - see changes in skull + femur + tibia

Rare 50yrs + 10% pop >80yrs)

37
Q

What is a rare complication of Paget’s?

A

OSTEOSARCOMA

  • most common in young
  • most malignant cancer
  • spreads RAPIDLY (to lungs)
  • in long bone (knee)
  • prevention = LIMB AMPUTATION
38
Q

Treatment for Paget’s

A

3 options:

  1. bisphosphonates
  2. Calcium + vit D supplements
  3. Calcitonin