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Metabolic Bone Disease Flashcards

1
Q

What are the functions of osteoblasts?

A

Build new bone matrix by working as a group
Move over matrix and make protein called osteoid (contains collagen)
Some osteoclasts become trapped in the bone are transformed into osteocytes

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2
Q

What are the functions of osteoclasts?

A

Breakdown bone

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3
Q

What is the function of PTH?

A

Stimulates the action of osteoclasts when low Ca in blood

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4
Q

When does PTH peak?

A

Middle of night, afternoon

Fluctuates minute to minutie

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5
Q

What does calcitonin do?

A

Slows activity of osteoclasts

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6
Q

Where is most Ca stored?

A

90% in bone

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7
Q

What other hormones impact the bone?

A

Oestrogen in females

Testosterone in men

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8
Q

What occurs during weight bearing exercise to the bone?

A

Bone production exceeds resorption and bones thicken

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9
Q

What other hormone increases bone mass?

A

GH

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10
Q

What hormone decreases bone mass?

A

Cortisol

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11
Q

What does RANKL do?

A

Allows T cells to bind to RANK protein on osteoclasts and activate them

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12
Q

What happens to vitamin D in the body?

A

UVB produces vit D
7-dihydrocholesterol is transformed by light into inactive vitamin D
Hydroxyl group is added to 7HDC in liver - this is the main storage form of vit D and what you should measure
Another hydroxyl group is added to the liver to make active vit D

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13
Q

Which group of people have less vitamin D?

A

Older people

People with darker skin - melanocytes absorb UVB so the paler you are, the less sunlight you need to make vit D

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14
Q

What two organs must be in tact to produce vit D?

A

Liver and kidney

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15
Q

What is the primary action of active vitamin D?

A

Absorb Ca from the gut

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16
Q

What is the pathophysiology of paget’s disease of the bone?

A

Localised disorder of bone turnover
Increase resorption, followed by increased bone formation, but replaced bone is v. weak and disorganised

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

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17
Q

What is the aetiology of Paget’s?

A

Strong genetic component (most purely genetic in origin)
15-30 familial
Loci of SQSTMI
Anglo-saxon origins
Environmental trigger - possibly chronic viral infection within osteoclast

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18
Q

What are the symptoms of Paget’s?

A

> 40yo patient
BONE PAIN
Occasionally bone deformity, excessive heat production over pagetic bone or by neurological complications, e.g. sensorineural deafness (due to compression of vestibulocochlear nerve) or conductive hearing loss (due to anklyosis of the ossicles)

Tends to stay in place it first manifests

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19
Q

What bony deformities are common in Paget’s?

A

Bowing of legs

Skull enlargement

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20
Q

What are the biochemical findings in Paget’s?

A

Normal PTH
Normal phosphate and Ca
Raised ALP

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21
Q

What is ALP a marker of?

A

OSTEOBLASTIC activity and also cholestasis

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22
Q

Give a stereotypical history of someone with Paget’s

A

50yo lady presents with bone pain, localised heat, bony deformity, hearing loss
Normal PTH, Ca, phos, raised ALP

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23
Q

What can rarely develop in pagetic bone?

A

Osteosarcoma

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24
Q

What do bone scans show in paget’s?

A

Dense areas

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25
How do you Rx Paget's?
Don't Rx if asymptomatic unless in skull | IV bisphonates therapy (e.g. one off zoledronic acid infusion)
26
What is ricket's/osteomalacia?
Severe nutritional vit D/ca deficiency that causes insufficient mineralisation & thus rickets in a growing child/osteomalacia in an adult when the epiphyseal growth plates have fused
27
What other organs in impaired in ricket's/osteomalacia?
Muscle function impaired in low vit D states
28
What biochemical findings would you see in ricket's/osteomalacia?
Low vit D, low Ca and phosphate, high ALP and PTH
29
What is the presentation of ricket's?
``` Knock knees, bendy legs Stunted growth Fontanelles dont close Cant maintain weight Slayed epiphyses - abnormalities at sides of ribs, wrists, ankles due to expanded growth plates FTT Poor rib development ``` More common in uncontrolled coeliac/darker skin
30
What is the presentation of osteomalacia?
No bony deformities can be seen | On XRay - microfractures, looser's zones
31
What are looser's zones?
Wide, transverse lucencies traversing part way through a bone
32
How do you Rx osteomalacia/Ricket's?
Vit D supplements
33
What is osteogenesis imperfecta?
Genetic disorder of connective tissue characterised by fragile bones from mild trauma and even acts of daily living Other non-bone clinical findings
34
What are the range of presentations with OI?
Prenatally fatal --> presenting in early 40s with osteoporosis Interfamilial variation too!
35
What does the genetic mutation in OI result in?
Defect in type 1 collagen
36
What are the four most common types of OI?
1 - milder form, when child starts to walk it is picked up, may be picked up in adulthood 2 - lethal by age 1 3 - progressive deforming with severe bone dysplasia and poor growth 4 - similar to type 1 but more severe
37
What are the other features of OI?
Growth deficiency Defective tooth formation (enamel wears away - dentigenesis imperfecta) Hearing loss Blue sclera - sclera wears away and can see other layers of the eye Scoliosis/barrel chest Ligamentous laxity - hypermobility common Easy bruising Fractures caused by minimal impact
38
What score is used to measure degree of hypermobility?
Beighton score
39
How do you manage OI?
Rx fractures, e.g. for leg fractures child can be put in extendable rods that grow with child IV bisphosphonates which help prevent fractures Educational/social adaptations e.g. not playing rugby, encourage swimming, getting out of school early Genetic counselling
40
What is osteoporosis?
Metabolic bone disease characterised by low bone mass and micro-archiectural deterioration of bone tissue, leading to enhanced bone fragility and consequent increase in fracture risk OR result on DXA scan
41
Why is osteoporosis important?
Risk of fracture
42
What is risk of fracture related to?
Age, BMD, falls, bone turnover
43
What are the signs and symptoms of osteoporosis?
NONE | silent condition in which bones become thinner and more fragile
44
What tool can be used to measure fracture risk?
FRAx
45
Describe FRAX risk assessment tool
Gives risk of fracture over next 10 years Uses: age, sex, weight, height, prev fracture, parent fractured hip, current smoking, glucocorticoids, RA, secondary osteoporosis, alcohol 3+ units/day, BMD
46
If risk is more than ____ from the FRAX score then _____
10% | refer for DXA scan
47
Why do you only want to diagnose osteoporosis when it is a problem?
Have to declare to insurance companies etc.
48
What does Q-fracture do?
Measures 10 year fracture risk For those 30-85, men and woman Variables: CV risks, falls, TCA Can't add BMD
49
What does DXA stand for?
Dual energy X-Ray absorptiometry
50
When should you get a DXA scan?
If FRAX score >10% | On oral steroids, suffer a low trauma fracture regardless of % risk
51
What does a DXA scan do?
Calculates BMD | Calculate a T score
52
What is a T score?
SD that the patients result is below the same young adult men (of same sex, race, BMI etc.)
53
What T score defines osteopenia?
-1-2.5
54
What T score defines osteoporosis?
55
What are the two types of DXA you can get?
Hips | Lateral
56
How common is osteoporosis?
1 in 2 woman >50 will have an osteoporotic fracture before they die (1 in 4 men) If you suffer vertebral fracture 5x more likely to have another & 2x as likely to have hip fracture
57
What are the endocrine causes of osteoporosis?
``` Thyrotoxicosis Hyper/hypoparathyroidism Cushings Hyperprolactinaemia Hypopituitarism Low sex hormone levels ```
58
What are the rheumatic causes of osteoporosis?
RA Ankylosing spondylitis Polymyalgia rheumatica (Rx steroids) NB inflammatory processes thin the bone
59
What are the GI causes of osteoporosis?
Inflammatory dx - UC/Crohn's Liver dx - PBC, CAH, alcoholic cirrhosis, viral cirrhosis (hep C) Malabsorption - CF, chronic pancreatitis, coeliac dx, whipple's, short gut syndromes, ischaemic bowel
60
What medications can cause osteoporosis?
``` Steroids PPIs Enzyme inducing anti-epileptics Aromatase inhibitors GnRH inhibitors Warfarin ```
61
How does our bone mass change with age?
Increase in size until mid-late 20s Accelerated loss after menopause Gradual loss in elderly In males gradual drop in testosterone allows bone receptors to adapt so there is less exaggerated bone loss
62
All individuals over 50 who have suffered a low trauma fracture should have what?
DXA scan
63
How can we prevent osteoporosis?
Minimise RFs Ensure good Ca and Vit D Falls prevention, e.g. physio Medications Ensure simple osteoporosis not due to myeloma, coeliac dx etc.
64
What medications can help with osteoporosis?
HRT - only in those with menopausal symptoms SERMs e.g. raloxifene, only help vertebral fractures Bisphoshonate (MAIN) Denosumab Teriparatide
65
What are the SEs of HRT?
Increased risk of blood clots Increased risk of breast cancer with extended use into late 50s/60s Increased risk of heart disease/stroke if used after large gap after menopause (>3y)
66
What are req for use of bisphosphonates?
Adequate renal function, Vit D and Ca status | Good dental health and hygiene - need regular chest ups
67
What are the SEs of bisphosphonates?
``` Oesophagitis Iritis/uveitis Not safe when eGFR <30mls/min ONJ (osteonecrosis of the jaw) Atypical femoral shaft fractures ``` Drug holiday? Take with water and sit upright
68
What is denosumab?
Monoclonal Ab against RANKL Reduces osteoclastic bone resportion S/c injection every 6 months Safer for those with renal impairment
69
What are the SEs of denosumab?
Allergy/rash Symptoamtic hypoCa if given and vit D deplete ONJ/atypical shaft fractures?
70
What is teriparatide?
Intermittent human parathyroid hormone | Stimulates osteoblasts to make bone
71
What are the SEs of teriparatide?
Injection site irritation Rarely hypercalcaemia Allergy Cost

MSK (27 decks)

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