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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
what other blood abnormality is seen in hypocalcaemia
raised phosphate
26
Tx of acute hypocalcaemia
Emergency | - IV 10% calcium gluconate 10 ml
27
what are causes of hypoparathyroidism
``` Congenital absence (DiGeorge syndrome) Destruction (surgery, radiotherapy, malign) Autoimmune Hypomagnesaemia Idiopathic ```
28
Mx of hypoparathyroidism
Calcium supplements 1-2g a day Vit D supplements tablets - 1alpha calcidol 0.5-1mcg injection - Cholecalciferol 300,000 units 6 monthly
29
what is calcium release from cells dependent on
magnesium
30
what is hypomagnesaemia
low Mg in the blood
31
what is seen in hypomagnesaemia
high intracellular calcium PTH release inhibited Skeletal and muscle receptors less sensitive to PTH
32
Tx of hypomagnesaemia
Magnesium salts
33
what causes hypomagnesaemia
``` Alcohol Drugs - thiazide, PPI GI illness - short gut Pancreatitis Malabsorption ```
34
what is Pseudohypoparathyoidism
genetic defect - dysfunction of G protein in GNAS1 | failure of target cell to respond to PTH
35
signs and symptoms of Pseudohypoparathyoidism
Brachydactyly - seen in 4th and 5th metacarpal of Round face Short stature Learning Disability
36
what is Brachydactyly
shortening of the fingers and toes due to unusually short bones
37
what are the test results of Pseudohypoparathyoidism
Decreased serum Calcium Increased PTH Alk phos normal or raised
38
what is Pseudo-pseudohypoparathyroidism
the morphological features of pseudohypoparathyroidism but with NORMAL BIOCHEMISTRY
39
can patents can from pseudo to pseudo-pseudo?
yes
40
what is osteomalacia know as in children
rickets
41
what can cause Rickets and Osteomalacia
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
what is osteomalacia
normal amount of bone but the mineral content is low | opposite of osteoporosis
43
symptoms of osteomalacia
``` bone pain and tenderness fractures esp femoral neck rib deformity limb deformity proximal myopathy dental defects ```
44
what x-ray sign is seen commonly in rickets and osteomalacia
Loosers zones | - pseudofractures
45
symptoms of rickets
growth retardation knock knees bow legs children are ill
46
lab results seen in rickets/osteomalacia
``` low calcium - often mild in rickets decrease phosphate increase alk phos PTH high decreased 25(OH) vit D ```
47
what does chronic renal disease cause in the body
vit D deficiency | secondary hyperparathyroidism
48
what are lab results seen in chronic renal disease
low 1,25-OH Vit D
49
Tx for rickets/osteomalacia
Vit D supplements
50
if vit D deficiency due to chronic renal disease what is the Tx
Alfacalcidol OR Calcitriol
51
what are side effects of Calcitriol and Alfacalcidol
can cause dangerous hypercalcaemia
52
what is vitamin D resistant rickets
X-linked hypophosphatemia (i.e. low phosphate levels) Defect in PHEX gene High Vit D levels
53
Ix findings of vitamin D resistant rickets
low phosphate high vit D phosphaturia - too much phosphorus in urine
54
Tx of vitamin D resistant rickets
Phosphate | Vit D supplements - Calcitriol
55
what is osteoporosis
progressive skeletal disease low bone mass deterioration of bone tissue increase in bone fragility and susceptibility to fracture
56
common fracture sites seen in osteoporosis
neck of femur vertebral body distal radius humeral neck
57
when is a patient assessed for risk factors of osteoporosis
Anyone >age 50 years with risk factors Anyone under 50 years with very strong clinical risk factors Early menopause Glucocorticoids
58
when to refer for DEXA
If there is a 10 year risk assessment for any OP fracture of at least 10%
59
what are risk factors for osteoporosis
SHATTERED Steroid use Hyperthyroidism/hyperparathyroidism Alcohol and tobacco use Thin (BMI
60
what are the BMD scores suggestive of bone pathology
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
what will the blood results be in osteoporosis
normal
62
Tx of osteoporosis
Biphosphonate Calcium and Vit D supplements Strontium ranelate - 3rd line HRT
63
what is given for premature osteoporosis
HRT or Testosterone
64
examples of biphosphonates and what do they do
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
why is Strontium ranelate third line and when is it contraindicated
- fracture risk reduction slightly less than bisphosphonate | - history of thromboembolic disease, IHD, peripheral arterial disease, uncontrolled hypertension
66
relationship between corticosteroids and bone
Reduction of osteoblast activity and lifespan Suppression of replication of osteoblast precursors Reduction in calcium absorption Inhibition of gonadal and adrenal steroid production
67
what is Paget's disease
increased bone turnover associated with increased numbers of osteoblasts and osteoclasts
68
what does Paget's disease cause
bone enlargement, deformity and weakness bone pain deafness compression neuropathies
69
blood chemistry of Paget's disease
alk phos very raised | normal calcium and phosphate
70
Tx of Paget;s
Analgesia | Is that fails bisphosphonates
71
what is osteogenesis imperfecta
genetic disorder of type I collagen | results in fragile, low density bones
72
what are the types of osteogenesis imperfecta
Type I - Mild Type III and IV - very severe Type II - neonatal lethal
73
what is osteogenesis imperfecta associated with
blue sclerae hearing loss dentinogenesis imperfecta - disorder of tooth development
74
how does the most severe form of osteogenesis imperfecta present
fractures in childhood | progressive spinal and limb deformity
75
when might mild osteogenesis imperfecta present
may not present till adult life
76
Tx of osteogenesis imperfecta
fracture fixation surgery to correct deformities bisphosphonates prevent injury

Endocrine SB (15 decks)

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