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Homeostasis > Calcium metabolism > Flashcards

Calcium metabolism Flashcards

1
Q

what effect does PTH have on Ca2+ and PO4

A

incr ca and decr po4

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2
Q

how does PTH affect calcium

A

decreases renal excretion and increases renal tubular reabsorption, releases Ca from bone by osteoclasts, and stimulates 1,25(OH)2D synthesis in kidney.

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3
Q

when is PTH released

A

in hypocalcaemia and hyperphosphataemia

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4
Q

what is the action of 1,25(OH)2D (calcitriol)

A

it is the active form and enhances intestinal absorption of calcium and PO4 for new bone formation. also- mineralisation of bone.

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5
Q

what is the normal value of calcium

A

2.2-2.6mmol/L

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6
Q

what are the 3 main causes of hypercalcaemia

A

cancer, chronic renal failure, primary hyperparathyroidism

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7
Q

what is the action of Mg

A

causes hypocalcaemia as prevents PTH release

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8
Q

what do the labs measure for calcium

A

total plasma Ca2+- 40% bound to albumin and the rest free ionised calcium

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9
Q

what are the clinical features of hypercalcaemia

A

’ bones, stones, groans and psychic moans’. neuro- lethargy, confusion, coma, psychosis, hypotonia. GI- anorexia, vomiting, constipation. renal- polyuria, polydipsia, dehydration, hypercalciuria, nephrocalcinosis. cardio- arrhythmias.

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10
Q

what happens on the ECG in hypercalcaemia

A

decr QT interval

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11
Q

what are the rarer causes of hypercalcaemia

A

immobilisation, thyrotoxicosis, vit D toxicity, lithium, sarcoidosis, hypoadrenalism

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12
Q

investigations hypercalcaemia

A

bone profile- ca, po4, albumin, ALP. FBC, ESR, liver profile, renal profile, TFTs, X rays. PTH and 25 (OH)D

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13
Q

where is vitamin D first hydroxylated and to what

A

liver- to 25-hydroxyl vit D

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14
Q

where is 1,25 hydroxyl vit D made

A

kidneys

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15
Q

how can you distinguish between malignancy and 1ary hyperparathyroidism

A

decr albumin in malignancy along with decr Cl-, alkalosis, decr K+, incr PO4, incr ALP.

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16
Q

what does an incr PTH indicate

A

hyperparathyroidism

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17
Q

if albumin is high and urea is raised what is the cause of the hypercalcaemia

A

dehydration

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18
Q

if the albumin is normal or low and phosphate is decr or normal what is the cause (hyper)

A

1ary or 3ary hyperparathyroidism

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19
Q

if the albumin is normal or low and phosphate is incr or normal what is the cause if ALP is raised

A

raised ALP- bone mets, sarcoidosis, thyrotoxicosis, lithium

20
Q

if the albumin is normal or low and phosphate is incr or normal what is the cause if ALP is normal

A

myeloma, sarcoidosis, vit D excess

21
Q

how to treat acute hypercalcaemia

A

dehydration- IV 0.9% saline; bisphosphonates- zoledronic acid, sodium clodronate, ibandronic acid; chemo; steroids

22
Q

how long does pamidronate take to work and reach max also what doses and side effects`

A

2-3 days, takes a week to reach max. 30mg in 300ml 0.9% saline over 3 hours. side effects- flu like symptoms, decr PO4, bone pain, myalgia, n & v

23
Q

what cancers are commonly assoc with tumour induced hypercalcaemia

A

lung, breast, renal, myeloma

24
Q

biochem tumour induced hypercalcaemia

A

suppressed PTH, hypoalbuminaemia, incr ESR, treat IV bisphosphonates, treat tumour

25
Q

what happens in chronic renal failure (hyper)

A

decr GFR. tertiary hyperparathyroidism. vit D metabolites (iatrogenic)/ parathyroidectomy if very high.

26
Q

what do the parathyroid glands secrete

A

1,84 PTH

27
Q

what happens to calcium and PO4 in primary hyperparathyroidism

A

ca incr, po4 incr- inappropriate

28
Q

what happens to calcium and PO4 in secondary hyperparathyroidism

A

ca decr, po4 incr- appropriate

29
Q

what happens to calcium and PO4 in tertiary hyperparathyroidism

A

after prolonged hypocalcaemia in secondary, get hypercalcaemia mimicking primary.

30
Q

which is less common hyper or hypocalcaemi

A

hypo

31
Q

causes of hypocalcaemia

A

hypoparathyroidism, pseudoparathyroidism, vit D deficiency, Mg deficiency, malabsorption, renal failure

32
Q

which causes are assoc with a raised PO4 (hypo)

A

CKD, hypoparathyroidism, pseudo, vit D deficiency, hypomagnesaemia

33
Q

which causes are assoc with a normal or decr PO4 (hypo)

A

osteomalacia, acute pancreatitis, over hydration, respiratory alkalosis

34
Q

when are the clinical features apparent in hyper and hypo

A

hyper >3 mmol/L. hypo 2 mmol/L

35
Q

clinical features hypocalcaemia

A

SPASMODIC- Spasms; Perioral parasthesiae; Anxious, irritable, irrational; Seizures; Muscle tone incr in smooth muscle- colic, wheeze, dysphagia; Orientation; Dermatitis; Impetigo; Chovsteks sign, choreoathetosis, cataract, cardiomegaly

36
Q

what are the signs in hypocalcaemia

A

Trosseaus- on inflating the cuff, wrist and fingers flex and draw together (carpopedal spasm). Chovstek- corner of mouth twitches when facial nerve is tapped over the parotid

37
Q

what is choreoathetosis

A

involuntary movements

38
Q

treatment of hypocalcaemia

A

mild- calcium 5mmol/L 6h PO with daily plasma Ca levels. in CKD may require alfacalcidol. severe- 10ml 10% calcium gluconate IV over 30 mins

39
Q

what can hypoparathyroidism be due to

A

auto immune or post thyroid surgery. PTH low. PO4 high creatinine normal.

40
Q

treat hypoparathyroidism

A

calcitriol and thiazides

41
Q

what is pseudohypoparathyroidism

A

rare inherited condition. defect in the PTH receptor with PTH resistance. incr PTH decr Ca incr PO4.

42
Q

what features do you get in pseudohypo

A

short stature, shortened metacarpals. intellectual disability and treat with calcitriol.

43
Q

what happens in hypomagnesaemia

A

parasthesiae, ataxia, seizures, tetany, arrhythmias,

44
Q

causes of hypomagnesaemia

A

diuretics, diarrhoea, ketoacidosis, alcohol, decr Ca, decr K, decr PO4. treat with Mg salts eg MgSO4

45
Q

what happens in hypermagneseamia

A

neuromusc depression, decr bp and pulse, hyporeflexia, CNS and resp depression, coma.

46
Q

causes of hypermagnesaemia

A

renal failure, iatrogenic. treat if severe >7.5 mmol/L

Homeostasis (14 decks)

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