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Systems: MSK AB > Metabolic Bone Disease > Flashcards

Metabolic Bone Disease Flashcards

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1
Q

What are the 2 main cells of bone remodelling?

A
  • Osteoblasts

- Osteoclasts

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2
Q

What type of cell do osteoblasts develop from?

A

Mesenchymal progenitor cell

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3
Q

What type of cell do osteoclasts develop from?

A

Myeloid progenitor cell

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4
Q

What is the role of osteoclasts?

A

Bone resorption

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5
Q

What is the role of osteoblasts?

A

Bone formation

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6
Q

How do osteoblasts control osteoclasts?

A
  • When stimulated they produce RANKL
  • RANKL binds to pre-osteoclasts
  • Activation of osteoclasts
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7
Q

What produces vitamin D?

A

UVB

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8
Q

Where is vitamin D stored?

A

Liver, fat and muscle

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9
Q

Where is vitamin D activated?

A

Kidney

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10
Q

In what form is vitamin D found in the skin?

A

7DHC

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11
Q

In what form is vitamin D found in the liver?

A

25(OH)vit D

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12
Q

In what form is vitamin D stored in the kidney?

A

1,25(OH)2 vit D

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13
Q

What happens to PTH when extracellular calcium is reduced?

A

Increases

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14
Q

What is Paget’s disease?

A
  • Localised disorder of bone turnover

- Increased bone resorption followed by increased bone formation

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15
Q

What does Paget’s disease lead to?

A

Disorganised bone: bigger, less compact, more vascular and mores susceptible to deformity and fracture

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16
Q

What is the aetiology of Paget’s disease?

A
  • Strong genetic component
  • 15-30% are familial
  • Loci of SQSTMI
  • Restricted geographic distribution: those of Anglo-Saxon origins
  • Environmental trigger: Possibility of chronic viral infection within Osteoclast
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17
Q

How does Paget’s disease present?

A
  • Patient>40 years
  • Bone pain
  • Bony deformity (occasional)
  • Excessive heat over Pagetic bone
  • Neurological complications (such as nerve deafness)
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18
Q

How is Paget’s investigated?

A

X-ray

  • Marked expansion of the bone
  • Dense and lucid areas

Bone scan
-Most useful definitive test

Isolated elevation of serum alkaline phosphotase

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19
Q

What can rarely develop from Paget’s?

A

Osteosarcoma in the affected bone

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20
Q

How is Paget’s disease treated?

A
  • No evidence to treat asymptomatic Paget’s unless in skull or in area requiring surgical intervention.
  • Do not treat based on a raised alkaline phosphatase alone
  • Intravenous Bisphosphonate therapy-One off zoledronic acid infusion
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21
Q

What is the difference between rickets and osteomalacia?

A
  • Rickets occurs in children before the epiphyseal plates fuse
  • Osteomalacia occurs in adults after the epiphyseal plates fuse
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22
Q

What causes rickets/osteomalacia?

A

Severe nutritional vitamin D or Calcium deficiency causes insufficient mineralisation and thus Rickets in a growing child and Osteomalacia in the adult when the epiphyseal lines are closed

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23
Q

What does vitamin D do?

A

Stimulates the absorption of calcium and phosphate from the gut and calcium and phosphate then become available for bone mineralisation

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24
Q

What effect doe low vitamin D have on muscle function?

A

Impaired function

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25
How does Rickets present in infants?
- Stunted growth - Bandy legs (once they start walking) - Splayed epiphyses - Large head (due to failure of fontanelles to close) - Nodules on sides of ribs - Failure to thrive - Fragile
26
What are the symptoms of osteomalacia?
- Bone pain - Muscle weakness - Increased falls risk
27
What develops in osteomalacia?
Microfractures
28
What is osteogenesis imperfecta?
- Genetic disorder of connective tissue characterised by fragile bones from mild trauma and even acts of daily life - Other non bone clinical features - Broad clinical spectrum
29
What is the cause of OI?
Defects in type I collagent (There are 8 types of OI in total with 1 to 4 being the most common)
30
Describe types 1-4 of OI.
- Type I: Milder form-when child starts to walk and can present in adults - Type II: Lethal by age 1 - Type III: Progressive deforming with severe bone dysplasia and poor growth - Type IV : Similar to type 1 but more severe
31
What non-skeletal features can OI present with?
- Growth deficiency - Defective tooth formation (dentigenesis imperfecta) - Hearing loss - Blue sclera - Scoliosis / Barrel Chest - Ligamentous laxity - Easy bruising
32
What scoring chart is used for hypermobility in OI?
Beighton score
33
How is OI managed?
- Surgical: to treat fractures - Medical: IV bisphosphonates to prevent fractures - Social: education and social adaptions - Genetic: genetic counselling for parents and next generation
34
How do we define osteoporosis?
A metabolic bone disease characterised by low bone mass and micro architectural deterioration of bone tissue, leading to enhanced bone fragility and a consequent increase in fracture risk
35
How is osteoporosis defined by DXA scan?
A result on DXA bone scanning <2.5 SDs below the young adult mean in a post-menopausal women (T score)
36
What is fracture in osteoporosis related to?
- Age - BMD - Falls - Bone turnover
37
How can we assess risk of osteoporotic fracture?
Q fracture score
38
What is Q fracture?
-Fracture risk score -Applicable to those aged 30-85 (men and women) -Contains multiple variables including CV risks, falls and TCAs -Cannot add BMD Some of the variable risks can not be altered by osteoporotic medications
39
What does a DXA scan of the spine look at?
- L2-L4 | - Thickening means secondary degenerative change has occurred
40
What does a DXA T score compare you to?
Young adult
41
What does a DXA Z score compare you o?
Peer of the same age
42
What should happen if someone's fracture risk from osteoporosis is deemed significant?
If the risk is consider significant ( normally defined as a >10% risk of osteoporotic fracture over 10 years) the individual should be referred for a DXA scan ( Dual energy X-ray Absorptiometry)
43
What should happen if someone is on oral steroids or has a low trauma fracture?
Should be referred for a DXA bone scan regardless of their fracture risk percentage
44
How common is osteoporosis?
- I in 2 women over 50 will have an osteoporotic fracture before they die - I in 5 men over 50 will suffer and osteoporotic fracture - A 50 year old woman has a lifetime risk of 17% of a hip fracture - If you suffer 1 vertebral fracture you are 5 times more likely to have another and twice as likely to have hip fracture than if you had no vertebral fractures.
45
What endocrine causes of osteoporosis are there?
- Thyrotoxicosis - Hyper and Hypoparathyroidim - Cushings - Hyperprolactinaemia - Hypopituitarism - Low sex hormone levels
46
What rheumatic causes of osteoporosis are there?
- Rheumatoid arthritis - Ankylosing Spondylitis - Polymyalgia Rheumatica
47
What GI causes of osteoporosis are there?
- Inflammatory diseases: UC and crohns - Liver diseases: PBC, CAH, Alcoholic cirrhosis, Viral cirrhosis (Hep C) - Malabsorption: Cystic Fibrosis, chronic pancreatitis, coeliac disease, whipples disease, short gut syndromes and ischaemic bowel
48
What medications can cause osteoporosis?
- Steroids - PPI - Enzyme inducting antiepileptic medications - Aromatase inhibitors (anti-oestrogens used in breast cancer) - GnRH inhibitors - Warfarin
49
How does our bone mass change with time?
- 0-20: increasing bone size - About 25: peak bone mass - Gradual decrease in bone mass - Accelerated bone loss when menopause begins - Gradual bone loss in the elderly
50
How do we prevent osteoporotic fractures?
- Minimise risk factors - Ensure good calcium and vitamin D status - Falls prevention strategies - Medications
51
What medication helps to prevent osteoporotic fractures?
- HRT: Oestrogen and testosterone - Selective oestrogen receptor modulator (raloxifene) SERM - Bisphosphonates
52
What are the side effects of HRT?
- Increased risks of blood clots - Increased risk of breast cancer with extended use into late 50s/early 60s - Increased risk of Heart disease and stroke if used after large gap from menopause (more than 3 year gap)
53
What are the negative effects of SERM?
- Hot flushes if taken close to menopause - Increased clotting risks - Lack of protection at hip site
54
What is the first line pharmacotherapy for fracture prevention in osteoporosis?
Oral bisphosphonates
55
What must be ensured before commencing oral bisphosphonates?
- Adequate renal function - Adequate calcium and vitamin D status - Good dental health and hygiene advised
56
What are the possible side effects of bisphosphonates?
- Oesophagitis - Iritis/uveitis - Not safe when eGFR<30 mls/min - Osteonecrosis of the jaw - Atypical femoral shaft fractures Drug holiday of 1-2 years after 10 years of use
57
What is Denosumab?
A monoclonal antibody against RANKL
58
How is denosumab used?
- SC injection every 6 months | - Safer in patients with significant renal impairment then bisphosphonates
59
What does denosumab do?
Reduces osteoclatic bone resportion
60
What are the possible side effects of denosumab?
- Allergy/rash - Symptomatic hypocalcaemia if given when vitamin D deplete - ?ONJ - ? Atypical femoral shaft fractures
61
What is teriparatide?
Part of PTH that purely stimulates osteoblasts
62
What are the side effects/disadvantages of teriparatide?
- Injection site irritation - Rarely hypercalcaemia - Allergy - COST

Systems: MSK AB (43 decks)

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