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Endocrinology > Calcium Homeostasis & Disorders > Flashcards

Calcium Homeostasis & Disorders Flashcards

1
Q

how is calcium homeostasis achieved & maintained?

A

diet
gut absorption
PTH
Vit. D

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2
Q

what affects gut absorption of calcium?

A

age
hormones
bowel pathology

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3
Q

what affects PTH levels?

A

hyper/hypoparthryroidism

malignant hypercalcaemia

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4
Q

what affects vit. D levels?

A 
diet 
absorption 
renal 
liver 
UVB exposure 
drugs
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5
Q

what kind of feedback controls calcium?

A

negative

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6
Q

what kind of receptors are present on the parathyroid gland for calcium?

A

G-protein coupled recepetor

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7
Q

what happens to PTH levels when calcium’s GPCR is activated?

A

PTH is suppressed

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8
Q

what does Vit. D do?

A

encourages calcium deposition in bones & suppresses PTH

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9
Q

what does PTH do?

A

increases calcium uptake, makes you store calcium in bones & prevents loss through kidneys

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10
Q

what are the acute symptoms of hypercalcaemia?

A

thirst, dehydration, confusion, polyuria

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11
Q

what are the chronic symptoms of hypercalcaemia?

A

myopathy, osteopaenia, fractures, depression, hypertension,

abdominal pain- pancreatitis, ulcers, renal stones

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12
Q

what are the 2 main causes of hypercalcaemia?

A

primary hyperparathyroidism

malignancy

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13
Q

what are some other causes of hypercalcaemia?

A

drugs
granulomatous disease
familial hypocalciuric hypercalcaemia
tertiary hyperparathyroidism

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14
Q

what drugs can cause hypercalcaemia?

A

vit D

thiazides

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15
Q

what biochemical picture do you need to diagnose hyperparathyroidism?

A

raised serum caclium
raised serum PTH
increased urine calcium excretion

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16
Q

what are the malignant mechanisms that can cause hypercalcaemia?

A
  • metastatic bone destruction
  • PTHrp from solid tumours
  • osteoclast activating factors
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17
Q

what is hypocalciuric hypercalcaemia?

A

autosomal dominant station that deactivates the calcium sensing receptor

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18
Q

how is hypocalciuric hypercalcaemia diagnosed?

A

Mild Hypercalaemia
Reduced urine calcium excretion
PTH may be (marginally) elevated
Genetic Screening

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19
Q

what is osteoporosis?

A

Progressive systemic skeletal disease characterised by low bone mass and microarchitectural deterioration of bone tissue, with a consequent increase in bone fragility and susceptibility to fracture

20
Q

what are the common fracture sites in osteoporosis?

A

neck of femur
vertebral body
distal radius
humeral neck

21
Q

what predicts fracture risk independently of other risk factors?

A

bone mineral density

22
Q

osteopenia

A

low bone mass

23
Q

name some endocrine secondary causes of osteoporosis

A

hyperthyroidism
hyperparathyroidism
Cushing’s disease

24
Q

name some gastrointestinal secondary causes of osteoporosis

A

coeliac disease
IBD
chronic liver disease
chronic pancreatitis

25
Q

name some respiratory secondary causes of osteoporosis

A

CF

COPD

26
Q

what are bisphosphonates?

A

anti-resorptive agents

27
Q

what do bisphophonates do?

A

prevent bone loss at all sites vulnerable to osteoporosis

28
Q

what are the long term concerns of bisphosphonate therapy?

A

osteonecrosis of the jaw
oesophageal Ca
atypical fractures

29
Q

what is denosumab?

A

fully human monoclonal antibody that targets and binds with high affinity and specificity to RANKL

30
Q

RANKL

A

receptor activator of nuclear factor-kB ligand

31
Q

what are the adverse effects of denosumab?

A

hypocalcaemia
eczema
cellulitis

32
Q

what are the direct effects of corticosteroids on bone?

A

reduction of osteoblast activity & lifespan
suppression of replication of osteoblast precursors
reduction in calcium absorption

33
Q

wha are the indirect effects of corticosteroids on bone?

A

inhibition of gonadal & adrenal steroid production

34
Q

what is page’s disease?

A

abnormal osteoclastic activity followed by increased osteoblastic activity

35
Q

what occurs in page’s disease?

A

abnormal bone structure with reduced strength & increased fracture risk

36
Q

what is osteogenesis imperfecta?

A

rare group of genetic disorders mainly affecting bone

37
Q

what are the 3 main causes of hypocalcaemia?

A

hypoparathyroidism
Vit. D deficiency
chronic renal failure

38
Q

what is the emergency treatment of acute hypocalcaemia?

A

IV calcium gluconate 10 ml, 10% over 10 mins (in 50ml saline or dextrose)

39
Q

name some causes of hypoparathyroidism

A 
Congenital absence (DiGeorge syndrome)
Destruction (surgery, radiotherapy, malign)
Autoimmune - most common
Hypomagnesaemia
Idiopathic
40
Q

why is magnesium important in calcium homeostasis?

A

calcium release from cells is dependent on magnesium

41
Q

what happens in magnesium deficiency

A

intracellular calcium is high & PTH release is inhibited

42
Q

what is pseudohypoparathyoridism?

A

genetic defect causing PTH resistance & resulting in low calcium but high PTH

43
Q

which gene is affected in pseudohypoparathyroidism?

A

GNAS 1

44
Q

what clinical signs occur in pseudohypoparathyroidism?

A 
bone abnormalities 
obesity 
subcutaneous calcification 
learning disability 
brachdactyly
45
Q

brachdactyly

A

shortening of 4th metacarpal

46
Q

what is pseudo-pseudohypoparathyroidism?

A

same as psuedohypoparathyroidism with normal calcium levels

Endocrinology (23 decks)

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