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Delta Med - Endocrinology > Endocrinology 3 - Bone Metabolism > Flashcards

Endocrinology 3 - Bone Metabolism Flashcards

1
Q

What is the function of Rank and Rank-ligand

A

RANK is released by osteoblasts and binds to multinucleated osteoclasts, causing activation and bone resorption.

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2
Q

What changes occur in post-menopausal bone remodelling?

A
  1. increased osteoclast numbers
  2. increased resorption depth
  3. Incomplete filling by new bone

Outcome is negative bone balance

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3
Q

What are 4 mechanisms for arriving at low bone mass?

A
  1. Low peak bone mass
  2. premature menopause
  3. accelerated loss post menopause
  4. senile bone loss
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4
Q

What is secreted by osteoclasts?

A

H+
Cathepsin K
TRAP

Seals itself with alpha-v-beta-3

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5
Q

What are examples of secondary causes of bone loss?

A 
Hypogonadism
Vitamin D deficiency
Hyperthyroidism
Hyperparathyroidism
Coeliac disease
Multiple myeloma (
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6
Q

What proportion of patients over 60y have OP?

A

60% of women

30% of men

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7
Q

What are the sequelae of hip fractures?

A

33% totally dependent or in nursing home

25% will die

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8
Q

Who should be treated for osteoporosis?

A

Patients with existing fragility fracture (post menopausal women, or men >50)
risk of fracture increases with each new fracture - 3-5x more likely to have another fracture, compared to those whom have never had a previous fracture

Asmyptomatic vertebral fractures

Treat others according to risk

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9
Q

What are features of vertebral fractures?

A

only 1/3 of fractures come to clinical attention
decreased patient QoL
Increased mortality
adds to fracture cascade
increased risk of further vertebral fractures, but also hip fractures.

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10
Q

What are current reimbursement criteria for the treatment of osteoporosis?

A

Must have T score 70 with nil other risk factors.

Risk of fracture doubles for each SD below 0 (T-score)

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11
Q

What are factors used in the FRAX score?

A 
Low BMD
Age
Previous fracture
Family Hx
Low body weight
smoking
rheumatoid arthritis
corticosteroid use
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12
Q

When should patients receiving corticosteroids be treated for OP?

A

When T-score is

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13
Q

When should patients taking aromatase inhibitors be treated for OP?

A

When T-score

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14
Q

Risk of what fracture type increases markedly with >7.5mg of prednisone/day?

A

spinal fractures

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15
Q

What are risk factors for glucocorticoid induced osteoporosis?

A 
Age - esp >60
Underlying disease - RA, PMR, IBD, COPD, transplant
Dose and duration of GC
Previous fracture
Low BMD
Low BMI (
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16
Q

What type of bone is predominantly lost in Glucocorticoid induced osteoporosis?

A

Cancellous bone - rapidly in the 1st year (6-12% loss), more slowly (3%) after that

Fractures occur in 30-50% of patients on long term GC

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17
Q

What are non-pharmacological measures in OP?

A

Falls prevention:

  • vision
  • proprioception
  • quadriceps strength
  • balance

Hip protectors - of no use in real world use

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18
Q

When is Vit D supplementation recommended, and at what dose?

A

Dietary intake is insufficient
Taking osteoporosis medication
Glucocorticoids >=7.5mg for >=3 months
Elderly, housebound or in residential care

500-600mg/day combine with supplementation if required (RDI is 1300mg/day in ostoporotic patients)

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19
Q

What are recommended doses of supplementation in deficiency of Vit D?

A

30-49 - mild deficiency - 1000-2000IU/day

12.5-29 - mod deficiency - 3000-4000units for 6-12 weeks, then 1000-2000IU maintance dose

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20
Q

What groups are at risk of vitamin D deficiency?

A 
High latitudes in winter
Elderly, particularly residential care
Conditions where sun avoidance is required
Dark skin
malabsorption
biliary cirrhotics
anti-epileptics
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21
Q

What is the mechanism of action of odanacatib?

A

cathepsin K inhibitor
prevents bone remodelling by inhibiting osteoclast resorptive activity.
Significant improvements in T score in patients

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22
Q

What is the mechanism of action of SERMS?

A

non-hormonal, selectively estrogen like in bone, and blocks estrogen in breast.
blocks differentiation of prefusion osteoclasts into activated osteoclasts.

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23
Q

What are outcomes for patients treated with SERMS?

A

Reduces vertebral fractures by 36% in postmenopausal women with osteoporosis.
Prevents breast cancer
Raloxifene does not prevent vertebral fractures.

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24
Q

What is the mechanism of action of bisphosphonates?

A

farnesyl pyrophosphate synthase inhibitors - loss of ruffled border and inhibition of vesicle trafficking, accelerated apoptosis.

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25
Q

What type of bone benefit most from the administration of bisphosphotates (Alendronate)

A

trabecular bone gains more than cortical, due to increased rate of bone turnover - hence lumbar spine more than hip/femoral neck etc.

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26
Q

What is the effect of alendronate on fractures?

A

47% reduction in new vertebral fractures, 51% reduction in hip fractures

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27
Q

What is the effect of zolendronate on fractures?

A

70% reduction in vertebral fractures, 41% reduction in hip fractures

significant increase in serious atrial fibrillation

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28
Q

What is the mechanism of action of denosumab?

A

denosumab is a monoclonal humanised anitibody which binds rank ligand and inhibits osteoclast formation, function and survival, limiting bone resorption.

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29
Q

What effect does denosumab have on BMD?

A

increase in BMD by 9.2% at lumbar spine

  1. 9% increase at trochanter
  2. 0% total hip
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30
Q

What effect does denosumab have on fractures?

A

68% reduction in new vertebral fractures
40% reduction in hip fractures
20% non-vertebral fractures

31
Q

What is the effect of stopping alendronate after 5 years of therapy?

A

No increase in fracture risk except for vertebral fracture risk.

32
Q

What is the effect of stopping zoledronic acid after 3 years vs 6 years of therapy?

A

Higher incidence of new vertebral fractures in the 3 year group, however no increase rate of other fractures, and slight decline in BMD, however still above pretreatment levels in 3 year group.

33
Q

What are features of atypical femoral fractures?

A 
stress fractures
BP therapy for average 7y
70% have prodrome
28% bilateral
26% delayed healing
concomitant GC use in 34%
Concomitant PPI use in 39%
34
Q

What are x-ray features of atypical femoral fractures?

A 
No comminution
Transverse at lateral cortex
Medial spike
Diffuse cortical thckening
Focal lateral thickening - beaking
35
Q

What is management of AFFs?

A

discontinue antiresorptive
prophylactic nail fixation if pain or cortical lucency
if no pain or cortical lucency - limited weight bearing until no oedema on MRI/bone scan (? teriparetide)
monitor the contralateral hip.

36
Q

What is the MoA of strontium ranelate?

A

stimulates osteoblasts, inhibits osteoclasts and increases tissue material strength.

37
Q

What effect does strontium have on BMD?

A

8.2% increase, however strontium affects DEXA scan, 1/2 is ‘real’ increase

38
Q

What effect does strontium ranelate have upon fractures?

A

49% reduction in vertebral fractures.

39
Q

What are AEs of strontium ranelate?

A

Diarrhoea
VTE
Eosinophilic syndrome (Rare)
Myocardial Infarction

(now 2nd line therapy)

40
Q

What is the effect of PTH when given once daily?

A

pulsed, once daily injection is anabolic for bone, vs continuous infusion which is catabolic. stimulates bone formation.

stimulates osteoblasts and later osteoclasts by Increase in RankL and decrease in OPG secretion from osteoblasts.

41
Q

What do mutations in LRP5 cause?

A

severe activating mutations cause severe osteoporosis/pseudoglioma.

activating mutations cause high bone mass - sterosclerosis

42
Q

What is the significance of LRP5?

A

LRP5/WNT/SOST pathway is a target for new skeletal anabolic treatments

43
Q

What is the effect of sclerostin in Wnt signalling?

A

sclerostin secreted by osteocyte causes inhibition of bone formation via osteoclasts.

44
Q

What is the typical presentation of osteomalacia?

A 
bone pain
fractures (typically stress)
myopathy (waddling gait)
elevated ALP
Check Ca, phosphate, 25OHD, PTH levels
Urinary phosphage (TmP/GFR)
Bone Bx may be required
45
Q

What are causes of osteomalacia?

A

Vitamin D Deficiency:

  • nutritional
  • malabsorption
  • liver disease
  • renal disease
  • nephrotic syndrome
  • anti-epileptics
  • genetic causes (VDR, CYP27B1, 25-hydroxylase)

Hypophosphataemia

  • Fanconi syndrome
  • Tumor related osteomalacia
  • Genetic causes (XLH, ADHR, ARHR, HHRH)
46
Q

What are humoral causes of renal phosphate wasting?

A 
FGS23 mediated:
TIO - mesenchymal tumours (paraneoplastic)
Iron Polymaltose
XLH
ADHR
ARHR
47
Q

What are renal causes of phosphate leakage?

A

Fanconi syndrome
HHRH
Anti-retrovirals

48
Q

What is the effect of FGF-23 on the kidney?

A

Increases urinary phosphate excretion and decreases Vit D production

49
Q

What are findings in tumour induced osteomalacia?

A

Hypophosphataemia, low TmP/GFR, low/N vit D, ALP often high.
Osteomalacia on bone Bx
Associated with mesenchymal tumours, also breast, prostate, SCLC, MM, CLL
Treatment: rocaltrol+/- phosphate, excision of tumour if fount

50
Q

What can be used to find tumours in TIO?

A

DOTATATE-PET

51
Q

How does perinatal, infantile or childhood hypophosphataemia present?

A

recurrent, slow healing metatarsal stress fractures
pseudofracture - proximal femur
chondrocalcinosis common, CPPD rare
50% have early loss of decidious teeth, rickets

52
Q

What is a treatment option in perinatal/infantile/childhood hypophosphataemia?

A

teriparetide

53
Q

What is the pathogenesis of paget’s disease?

A

significantly increased osteoclast activity with commensurate increase in activity from osteoblasts, new bone formed is abnormal.

54
Q

What are the outcomes of paget’s disease?

A 
increased overall bone turnover
thickened and weakened existing bone
severe pain in affected bone
bone overgrowth may affect nerves
sarcoma rarely in affect bones
55
Q

What are clinical manifestations of skeletal disease in paget’s disease?

A 
bone pain, nocturnal
bone deformity
OA of adjacent joints
fractures
spinal stenosis
56
Q

What are investigations in paget’s disease?

A

ALP increased
X-ray
Bone scan

57
Q

When is treatment for paget’s disease indicated?

A 
Bone pain
involvement of petrous temporal bone
nerve or spinal cord compression
cardiac failure
involvement of critical bone
cosmetic change
bending of femur or tibia
58
Q

What is therapy of paget’s disease?

A

bisphosphonate
calcitonin
analgesics
surgery

59
Q

What is the biology in congenital paget’s?

A

activating mutations in RANK causes familial exapansile osteolysis
OPG mutation causes juvenile paget’s like disease
Mutation in sequestosome-1 causes familial paget’s disease

60
Q

What is the most common cause of hypercalcaemia in primary care?

A

primary hyperparathyroidism

malignancy often in hospitalised patients

61
Q

What are PTH dependent causes of hypercalcaemia?

A

Hyperparathyroidism (primary or secondary)

Abnormality of the CaSR - familial hypocalciuric hypercalcaemia, autoimmune hypercalcaemia

62
Q

What are medications that cause hypercalcaemia?

A

lithium
thiazides
calcitriol
CaCO3 and antacids

63
Q

What are PTH independent causes of hypercalcaemia?

A

Cancer - myeloma, PTHrP, Osteolytic mets, 1,25(OH)2D
Excess calcitriol - sarcoid, granulomatous disease
Excess gastrointestinal calcium - milk alkali syndrome
Endocrine - thyrotoxicosis, phaeo, cortisol def, VIPoma
Immobilisation

64
Q

What are appropriate initial tests in hypercalcaemia?

A 
Serum calcium, albumin, ionised ca
PTH
25OHD
Creatinine
Urinary Calcium
65
Q

What imaging should be performed if a patient is a surgical candidate for hypercalcaemia?

A

Parathyroid sestaMIBI

Parathyoid uss

66
Q

When is surgery indicated in primary hyperparathyroidism?

A

Calcium >0.25 above ULN
CrCl 400 and/or nephrocalcinosis
BMD - T-score

67
Q

What are skeletal complications of PHPT?

A 
low BMD
#
osteitis fibrosa cystica
brown tumours
subperiostial resoprtion of phalanges
tapering of distal clavicles
salt and pepper skull
68
Q

What are benefits of parathyroid surgery?

A

In RCTs - improved BMD at hip and LS, with improved QoL

Observational - improved Sx, reduced nephrocalcinosis, improved BMD, reduced # risk

69
Q

What is the role of bisphosphonates in PHPT?

A

significant improvement in LS BMD, NS difference in total Hip.
NO change in serum calcium, PTH, urinary calcium

70
Q

What is the significance of Vit D in PHPT?

A

ensure that patients are vit D replete, as clinical severity of PHPT is higher with low vit D.
increased risk of hungry bone syndrome/hypocalcaemia post PTectomy in vit d deficient patients

71
Q

What malignancies are associated with PTHrP?

A

SCC, renal, ovarian, breast, endometrial

72
Q

What malignancies are associated with osteolysis?

A

Breast, MM, lymphoma

73
Q

What malignancies increase vitamin D?

A

Lymphoma.

Delta Med - Endocrinology (4 decks)

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