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Endocrine SB > Calcium Homeostasis and Bone Disorders > Flashcards

Calcium Homeostasis and Bone Disorders Flashcards

1
Q

what contributes to calcium homeostasis

A

diet
gut absorption
PTH
Vit D

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2
Q

what are the 4 key components of calcium homeostasis

A

serum calcium, serum phosphate, 1,25-dihydroxyvitamin D-3 (vit D) and PTH

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3
Q

why does serum phosphate play a part

A

99% of the total body calcium is stored in bone in the form of phosphate and hydroxide salts

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4
Q

how is vitamin D made

A 
Dehydro-cholesterol
>> from sunlight
Cholecalciferol (D3)
>> converted in the liver
25 (OH) Vit D
>> converted in the kidney
1,25 (OH) Vit D
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5
Q

what is the primary action of Vit D

A

promote gut absorption of calcium

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6
Q

what are the other roles of Vit D

A

works in conjunction with PTH

increase of Vit D causes increase in calcium transport within the intestine, bone, and kidney

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7
Q

symptoms of hypercalcaemia

A

Stones, groans, bones, psychic moans

Acute - Thirst, dehydration, confusion, polyuria

Chronic - myopathy, osteopenia, fractures, depression, hypertension, pancreatitis, ulcers, renal stones

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8
Q

if you can do one test with suspected hypercalcaemia what is it

A

PTH levels

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9
Q

what does high PTH levels suggest

A

hyperparathyroidism is the cause of the hypercalcaemia

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10
Q

what are causes of hypercalcaemia

A
  • Primary hyperparathyroidism
  • Malignancy
  • Drugs - Vit D, Thiazides
  • Granulomatous Disease e.g. TB, Sarcoid
  • Familial Hypocalciuric hypercalcaemia
  • Tertiary hyperparathyroidism
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11
Q

what is suggestive of hyperparathyroidism

A

Raised serum Calcium
Raised serum PTH (or inappropriately normal)
Increased urine calcium excretion

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12
Q

why do you get hypercalcaemia in malignancy

A

Metastatic Bone destruction
PTHrp from solid tumours
Osteoclast activating factors

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13
Q

what is suggestive of malignancy

A

raised calcium and alk phosphatase

decreased albumin

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14
Q

Ix for malignancy causing hypercalcaemia

A

Isotope bone scan

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15
Q

Acute Tx of hypercalcaemia

A

IV fluids
Consider loop diuretics once rehydrated
Bisphosphonates e.g. Pamidronate

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16
Q

what are function of bisphosphonates

A

prevent bone reabsorption by inhibiting osteoclast activity

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17
Q

what genetic syndromes are linked with hypercalcaemia

A 
MEN 1/2
Familial hyperparathyroidism (FHPT)
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18
Q

what is Familial Hypocalciuric Hypercalcaemia

A

condition that can cause hypercalcemia
reduced calcium in urine
usually due to fault in Ca sensing receptor

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19
Q

why do you get hypercalcaemia in Familial Hypocalciuric Hypercalcaemia

A

perceived lack of calcium levels by the parathyroid leads to constitutively high levels of parathyroid hormone, and therefore hypercalcemia

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20
Q

what does PTH do

A

increases calcium resorption from the bone and increases phosphate excretion from the kidney which increases serum calcium and decreases serum phosphate.

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21
Q

what are symptoms of Hypocalcaemia

A 
Paraesthesia - fingers, toes, perioral
Muscle cramps and weakness
Fatigue 
Bronchospasm or Laryngospasm
Fits
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22
Q

what are signs of hypocalcaemia

A

Chovsteks sign
- corner of the mouth twitches when the facial nerve is tapped over the parotid

Trousseau’s sign
- in inflating the cuff, the wrist and fingers flex and draw together

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23
Q

what are signs on an ECG of hypocalcaemia

A

QT prolongation

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24
Q

causes of hypocalcaemia

A

Hypoparathyroidism
Vit D Deficiency (osteomalacia, rickets)
Chronic renal failure

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25
Q

what other blood abnormality is seen in hypocalcaemia

A

raised phosphate

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26
Q

Tx of acute hypocalcaemia

A

Emergency

- IV 10% calcium gluconate 10 ml

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27
Q

what are causes of hypoparathyroidism

A 
Congenital absence (DiGeorge syndrome)
Destruction (surgery, radiotherapy, malign)
Autoimmune
Hypomagnesaemia
Idiopathic
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28
Q

Mx of hypoparathyroidism

A

Calcium supplements 1-2g a day

Vit D supplements
tablets - 1alpha calcidol 0.5-1mcg
injection - Cholecalciferol 300,000 units 6 monthly

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29
Q

what is calcium release from cells dependent on

A

magnesium

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30
Q

what is hypomagnesaemia

A

low Mg in the blood

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31
Q

what is seen in hypomagnesaemia

A

high intracellular calcium
PTH release inhibited
Skeletal and muscle receptors less sensitive to PTH

32
Q

Tx of hypomagnesaemia

A

Magnesium salts

33
Q

what causes hypomagnesaemia

A 
Alcohol
Drugs - thiazide, PPI
GI illness - short gut
Pancreatitis
Malabsorption
34
Q

what is Pseudohypoparathyoidism

A

genetic defect - dysfunction of G protein in GNAS1

failure of target cell to respond to PTH

35
Q

signs and symptoms of Pseudohypoparathyoidism

A

Brachydactyly - seen in 4th and 5th metacarpal of
Round face
Short stature
Learning Disability

36
Q

what is Brachydactyly

A

shortening of the fingers and toes due to unusually short bones

37
Q

what are the test results of Pseudohypoparathyoidism

A

Decreased serum Calcium
Increased PTH
Alk phos normal or raised

38
Q

what is Pseudo-pseudohypoparathyroidism

A

the morphological features of pseudohypoparathyroidism but with NORMAL BIOCHEMISTRY

39
Q

can patents can from pseudo to pseudo-pseudo?

A

yes

40
Q

what is osteomalacia know as in children

A

rickets

41
Q

what can cause Rickets and Osteomalacia

A

Vit D deficiency due to

  • Dietary deficiency
  • Malabsorption: gastric surgery, coeliac disease, liver disease, pancreatic failure
  • Chronic renal failure
  • Lack of sunlight
  • Drugs eg anticonvulsants
42
Q

what is osteomalacia

A

normal amount of bone but the mineral content is low

opposite of osteoporosis

43
Q

symptoms of osteomalacia

A 
bone pain and tenderness
fractures esp femoral neck
rib deformity
limb deformity 
proximal myopathy 
dental defects
44
Q

what x-ray sign is seen commonly in rickets and osteomalacia

A

Loosers zones

- pseudofractures

45
Q

symptoms of rickets

A

growth retardation
knock knees
bow legs
children are ill

46
Q

lab results seen in rickets/osteomalacia

A 
low calcium - often mild in rickets
decrease phosphate 
increase alk phos
PTH high
decreased 25(OH) vit D
47
Q

what does chronic renal disease cause in the body

A

vit D deficiency

secondary hyperparathyroidism

48
Q

what are lab results seen in chronic renal disease

A

low 1,25-OH Vit D

49
Q

Tx for rickets/osteomalacia

A

Vit D supplements

50
Q

if vit D deficiency due to chronic renal disease what is the Tx

A

Alfacalcidol
OR
Calcitriol

51
Q

what are side effects of Calcitriol and Alfacalcidol

A

can cause dangerous hypercalcaemia

52
Q

what is vitamin D resistant rickets

A

X-linked hypophosphatemia (i.e. low phosphate levels)
Defect in PHEX gene
High Vit D levels

53
Q

Ix findings of vitamin D resistant rickets

A

low phosphate
high vit D
phosphaturia - too much phosphorus in urine

54
Q

Tx of vitamin D resistant rickets

A

Phosphate

Vit D supplements - Calcitriol

55
Q

what is osteoporosis

A

progressive skeletal disease
low bone mass
deterioration of bone tissue
increase in bone fragility and susceptibility to fracture

56
Q

common fracture sites seen in osteoporosis

A

neck of femur
vertebral body
distal radius
humeral neck

57
Q

when is a patient assessed for risk factors of osteoporosis

A

Anyone >age 50 years with risk factors
Anyone under 50 years with very strong clinical risk factors
Early menopause
Glucocorticoids

58
Q

when to refer for DEXA

A

If there is a 10 year risk assessment for any OP fracture of at least 10%

59
Q

what are risk factors for osteoporosis

A

SHATTERED

Steroid use
Hyperthyroidism/hyperparathyroidism
Alcohol and tobacco use
Thin (BMI

60
Q

what are the BMD scores suggestive of bone pathology

A

Osteopenia BMD > 1 SD below mean

Osteoporosis BMD > or equal to 2.5 SD below mean

Severe Osteoporosis BMD > or equal to 2.5 below mean with fragility fractures

61
Q

what will the blood results be in osteoporosis

A

normal

62
Q

Tx of osteoporosis

A

Biphosphonate
Calcium and Vit D supplements
Strontium ranelate - 3rd line
HRT

63
Q

what is given for premature osteoporosis

A

HRT or Testosterone

64
Q

examples of biphosphonates and what do they do

A

Alendronate or Risedroante

Are anti-resorptive agents
Prevent bone loss at all sites vulnerable to osteoporosis
Ingested by osteoclasts leading to cell death thereby inhibiting bone resorption

65
Q

why is Strontium ranelate third line and when is it contraindicated

A
  • fracture risk reduction slightly less than bisphosphonate

- history of thromboembolic disease, IHD, peripheral arterial disease, uncontrolled hypertension

66
Q

relationship between corticosteroids and bone

A

Reduction of osteoblast activity and lifespan
Suppression of replication of osteoblast precursors
Reduction in calcium absorption
Inhibition of gonadal and adrenal steroid production

67
Q

what is Paget’s disease

A

increased bone turnover associated with increased numbers of osteoblasts and osteoclasts

68
Q

what does Paget’s disease cause

A

bone enlargement, deformity and weakness
bone pain
deafness
compression neuropathies

69
Q

blood chemistry of Paget’s disease

A

alk phos very raised

normal calcium and phosphate

70
Q

Tx of Paget;s

A

Analgesia

Is that fails bisphosphonates

71
Q

what is osteogenesis imperfecta

A

genetic disorder of type I collagen

results in fragile, low density bones

72
Q

what are the types of osteogenesis imperfecta

A

Type I - Mild
Type III and IV - very severe
Type II - neonatal lethal

73
Q

what is osteogenesis imperfecta associated with

A

blue sclerae
hearing loss
dentinogenesis imperfecta - disorder of tooth development

74
Q

how does the most severe form of osteogenesis imperfecta present

A

fractures in childhood

progressive spinal and limb deformity

75
Q

when might mild osteogenesis imperfecta present

A

may not present till adult life

76
Q

Tx of osteogenesis imperfecta

A

fracture fixation
surgery to correct deformities
bisphosphonates
prevent injury

Endocrine SB (15 decks)

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