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pathology 2 > calcium > Flashcards

calcium Flashcards

1
Q

4 functions of calcium

A
  • protein function
  • function of sodium channels
  • muscle contraction
  • structure of bone and teeth
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2
Q

hypercalcaemia consequences

A
  • urolithiasis - renal impairment
  • arryhtemias
  • muscle weakness
  • drowsiness, confusion etc
  • constipation, abdominal pain
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3
Q

hypocalcaemia consequences

A
  • paraesthesias
  • hyperrflexia, tetany
  • cardiac arrythemias
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4
Q

why do some people need calcitriol suppliments

A

because if they have defective PTH or bad kidneys they can’t convert precursors to the final product

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5
Q

total calcium

A

unadjusted - abnormal albumin levels may change this

albumin adjusted - adjusted for if the albumin were normal

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6
Q

ionised calcium

A

uncorrected - good if minimal delay from collection to analysis
pH corrected - assumes true patient pH of 7.4

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7
Q

difference between total and ionised calcium

A

ionised calcium interacts with receptors

protein bound calcium does not

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8
Q

normal albumin level

A

40g/L

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9
Q

when is ionised calcium useful

A

truer picture of calcium metabolism as free calcium participates in metabolic pathways
or if total calcium can be adjusted
or for suspicion of mild PHPT with high-normal total calcium
presence of non-albumin plasma protein in higher concentrations than usual

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10
Q

downsides of ionised calcium

A

more expensive, special collection requirements, pH-related stability issues

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11
Q

what happens to the pH of a blood sample after collection

A

before separation of cells from plasma
- RBC metabolism produces acid, lowering pH
if there is space or the cap is off, carbon dioxide is lost causing pH to raise
only matters for pH, gases and ionised calcium

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12
Q

why does pH effect ionised calcium

A

H+ and Ca2+ compete for the same binding site on albumin

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13
Q

parathyroid hormone

A

if inappropriately normal or high - hypercalcaemia is PTH mediated
if low - non-PTH mediated hypercalcaemia

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14
Q

PTH-mediated hypercalcaemia

A
  • primary hyperparathyroidism - parathyroid adenoma/carcinoma, may be associated with familial syndrome
  • tertiary hyperparathyroidism
  • familial hypocalciuric hypercalcaemia
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15
Q

non PTH-mediated

A

malignancy - bone disease, humeral hypercalaemica malignancy (PTH-rp)

  • vit D intoxication
  • granulomatous disease
  • hyperthyroidism due to increase of bone turnover
  • thiazides
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16
Q

primary hyperparathyroidism

A
  • autonomous PTH secretion by parathyroid adenoma or hyperplasia
  • manifestations - none (common), osteoporosis, nephrolithiasis, GI symptoms, CNS disturbance
  • differential diagnosis - lithium therapy, familial hypocalciuric hypercalcaemia
17
Q

secondary hyperparathyroidism

A

secondary to low calcium (calcium concentration may be normal because its compensated)

  • vit D deficiency
  • impaired GI absorption
  • loop diuretics

secondary to hyperphosphataemia
- CKD

18
Q

hypoparathyroidism causes

A
  • parathyroid surgery
  • autoimmune
  • infiltration - haemochromatosis, wilson’s, granulomatous disease)
  • idiopathic
  • hypomagnesaemia
19
Q

hypomagnesaemia causes

A 
GI losses - diarrhoea 
acute pancreatitis - fat saponification 
renal losses 
- loops and thiazide diuretics 
- hypercalcaemia - competition for reabsorption in thick ascending limb 
- gitelman syndrome 
- familial syndromes 
- impaired absorption by proton pump inhibitor
20
Q

refeeding syndrome

A
  • hypophosphataemia is a hallmark
  • hypomagnesaemia, hypokalaemia occur by same mechanisms - intracellular shift due to insulin action, increased metabolic demand in carbohydrate metabolism
  • acute thiamine depletion
  • risk is greatly increased in whole body depletion states - chronic malnutrition vs 3 days of fasting
21
Q

hypophosphataemia causes

A
  • referring syndrome, hyperparathyroidism, vit D deficiency, diuretics
22
Q

hypophosphataemia consequences

A
  • muscle weakness, rhabdomyolysis
  • haematological abnormaliities
  • encephalopathy, seizures, coma
  • osteomalacia
23
Q

phosphate homeostasis

A

phosphate complexes wth calcium, preventing calcium interacting with CaSR

24
Q

hyperphophataemia causes

A

acute kidney injury or chronic kidney disease

  • tumour lysis syndrome
  • rhabdomyolysis
  • hypoparathyroidism
  • acromegaly
  • vit D toxicity
25
Q

hyperphosphataemia consequences

A

secondary hyperthyroidism
ectopic calcification
renal stones
calciphylaxis

pathology 2 (47 decks)

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