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Endocrine > Disorders of Calcium Homeostasis > Flashcards

Disorders of Calcium Homeostasis Flashcards

1
Q

what substances are involved in calcium metabolism?

A 
parathyroid hormone (PTH)
vitamin D
calcitonin
1 o-hydroxylase
25 hydroxylase
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2
Q

what stimulates most parathyroid hormone release?

A

low calcium
via calcium-sensing receptor (C ASR) in parathyroid
G protein coupled receptor

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3
Q

bone metabolism??.

A

…….

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4
Q

how does vitamin D resistant rickets develop?

A

inhibiting factors in the vitamin D pathway
- elderly immigrant
- pigmented sunscreen
- anticonvulsants
- renal disease
can inhibit the production and conversion of vitamin D into 1,25 OHD

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5
Q

general features of hypercalcaemia?

A

bones
stones
abdominal groans
psychic moans

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6
Q

acute hypercalcaemia features?

A

thirst
dehydration
confusion
polyuria

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7
Q

chroic hypercalaemia features?

A 
myopathy
fractures
osteopaenia
depression
hypertension
pancreatitis
DU
renal calculi
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8
Q

best test for hypercalcaemia?

A

PTH

- high = parathyroid issue

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9
Q

how can PTH be used to determine the underlying cause of hypercalcaemia?

A 
if PTH is high
- primary/tertiary hyperparathyroidism
- FHH
if PTH is low (high phosphate)
- bone pathology
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10
Q

what are the 2 main causes of hypercalcaemia?

A

primary hyperparathyroidism

malignancy

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11
Q

other causes of hypercalcaemia?

A

drugs: vit D, thiazides
granulomatous disease
familial hypocalcuric hypercalcaemia
high turnover disease (e.g pagets, thyrotoxicosis)

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12
Q

what are the features of primary hyperparathyroidism?

A

raised serum calcium
raised serum PTH (or inappropriately normal)
increased urine calcium excretion (ensure vit D replete)

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13
Q

how can malignancy cause hypercalcaemia?

A

metastatic bone destruction
PTH from tumour
osteoclast activating factors

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14
Q

how is hypercalcaemia of malignancy diagnosed?

A

raised calcium and alk phos
X ray, CT, MRI
isotope bone scan

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15
Q

treatment of acute hypercalcaemia?

A 
fluids
loop diuretics
bisphosphonates
steroids (e.g for sarcoidosis)
salmon calcitonin (rarely used)
chemotherapy if due to malignancy
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16
Q

what test can show uptake by parathyroid scan and when is it used?

A

sestamibi scan

use if intention of removing glands

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17
Q

how is primary hyperparathyroidism managed?

A

definitive = surgery
cinacalet
- mimics calcium
- good if unfit for surgery

18
Q

what are the indications for a parathyroidectomy?

A 
end organ damage
- bone disease 
- gastric ulcers
- renal stones
- osteoporosis
very high calcium (>2.85mmol/L)
under 50
eGFR <60mL/min
19
Q

primary vs secondary vs secondary hyperparathyroidism biochemistry features?

A 
primary = high calcium and PTH
secondary = low calcium, high PTH
tertiary = high calcium and PTH
20
Q

name 2 genetic syndromes which can cause hyperparathyrodisim?

A

MEN1/2
- usually causes parathyroid adenoma with hypercalcaemia
Familial isolated hyperparathyroidism
- adenoma as in primary hyperparathyroidism

21
Q

what is familial hypocalciuric hypercalcaemia?

A

autosomal dominant deactivating mutation in the calcium sensing receptor
usually benign/asymptomatic

22
Q

how is familial hypocalciuric hypercalcaemia diagnosed?

A

mild hypercalcaemia
reduced calcium excretion
marginally elevated PTH
genetic screening

23
Q

what are the symptoms and signs of hypocalcaemia?

A 
paraethesia
muscle cramps, tetany
muscle weakness
fatigue
bronchospasm or laryngospasm
fits
chovsteks sign
trousseau sign
QT prolongation on ECG
24
Q

how is acute hypocalcaemia managed?

A

emergency

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

25
Q

what can cause hypoparathyroidism?

A 
congenital absence (di George)
destruction
autoimmune
hypomagnesaemia
idiopathic
26
Q

what is the long term management for hypoparathyroidism?

A

calcium supplements
Vit D tablets
- 1 alphacalcidol
- depot injection (cholecaliferol)

27
Q

what are the effects of hypomagnesia?

A

calcium release from cells is dependant on magnesium so intracellular calcium is high in hypomagnesaemia
PTH release is inhibited
skeletal and muscle receptors are less sensitive to PTH
replace with calcium and magnesium

28
Q

what can cause hypomagnesia?

A 
alcohol
drugs
thiazide
PPI
GI illness
pancreatitis
malabsorption
29
Q

what is pseudohypoparathyroidism?

A

genetic defect of GNAS1 gene causing dysfunction of G protein

30
Q

what is pseudo-pseudohypoparathyroidism?

A

Albright’s hereditary osteodystrophy

but no alteration in PTH action and thus normal calcium

31
Q

what conditions are associated with vitamin D deficiency?

A

rickets

osteomalacia

32
Q

what can cause vitamin D deficiency?

A 
dietary deficiency/malabsorption
- gastric surgery
- coeliac disease
- liver disease
- pancreatic failure
chronic renal failure
lack of sunlight
drugs (anticonovulstants)
33
Q

what are the clinical features of osteomalacia?

A 
low calcium
muscle wasting (proximal myopathy)
dental defects
bone - tenderness, fractures, rib deformity, limb deformity
34
Q

loosers zone?

A

transverse lucencies traversing partway through a bone, usually at right angles with the cortex
associated with osteomalacia and rickets

35
Q

what can chronic renal disease cause?

A

vit D deficiency
- high 25-OH vit D
- can have low 1-25 OH vit D (useable)
secondary hyperparathyroidism

36
Q

treatment of vit D deficiency due to chronic renal disease?

A

titrate treatment to PTH levels

37
Q

name 2 long term consequences of vitamin D deficiency

A 
bone disease
- demineralisation/fractures
- osteomalacia/rickets
malignancy (esp colon)
heart disease
diabetes
38
Q

how is chronic vitamin D deficiency managed?

A

vitamin D3 tablets
calcitriol
alfacalcidol
combined calcium + vitamin D (e.g adcal D3)

39
Q

what are the features of pseudohypoparathyroidism?

A 
low calcium but PTH is high due to PTH resistance
bone abnormalities (McCune Albright)
Obesity
Subcutaneous calcification
learning disability
Brachdactyly (4th metacarpal)
40
Q

what can cause vitamin D resistant rickets?

A

hypophosphataemia due to X linked PHEX or FGF23 gene mutation

41
Q

what happens in vitamin D resistant rickets?

A

FGF 23 regulates phosphate levels in plasma and is secreted by osteocytes in response to calcitrol - can be dysfunctional in vit D resistant rickets
low phosphate
high vitamin D

42
Q

how is vitamin D resistant rickets managed?

A

phosphate and Vit D supplements (1,25-OH vit D3)

with or without surgery

Endocrine (45 decks)

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