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Flashcards in Calcium metabolism Deck (46):
1

what effect does PTH have on Ca2+ and PO4

incr ca and decr po4

2

how does PTH affect calcium

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

3

when is PTH released

in hypocalcaemia and hyperphosphataemia

4

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

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

5

what is the normal value of calcium

2.2-2.6mmol/L

6

what are the 3 main causes of hypercalcaemia

cancer, chronic renal failure, primary hyperparathyroidism

7

what is the action of Mg

causes hypocalcaemia as prevents PTH release

8

what do the labs measure for calcium

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

9

what are the clinical features of hypercalcaemia

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

10

what happens on the ECG in hypercalcaemia

decr QT interval

11

what are the rarer causes of hypercalcaemia

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

12

investigations hypercalcaemia

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

13

where is vitamin D first hydroxylated and to what

liver- to 25-hydroxyl vit D

14

where is 1,25 hydroxyl vit D made

kidneys

15

how can you distinguish between malignancy and 1ary hyperparathyroidism

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

16

what does an incr PTH indicate

hyperparathyroidism

17

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

dehydration

18

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

1ary or 3ary hyperparathyroidism

19

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

raised ALP- bone mets, sarcoidosis, thyrotoxicosis, lithium

20

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

myeloma, sarcoidosis, vit D excess

21

how to treat acute hypercalcaemia

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

22

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

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

what cancers are commonly assoc with tumour induced hypercalcaemia

lung, breast, renal, myeloma

24

biochem tumour induced hypercalcaemia

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

25

what happens in chronic renal failure (hyper)

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

26

what do the parathyroid glands secrete

1,84 PTH

27

what happens to calcium and PO4 in primary hyperparathyroidism

ca incr, po4 incr- inappropriate

28

what happens to calcium and PO4 in secondary hyperparathyroidism

ca decr, po4 incr- appropriate

29

what happens to calcium and PO4 in tertiary hyperparathyroidism

after prolonged hypocalcaemia in secondary, get hypercalcaemia mimicking primary.

30

which is less common hyper or hypocalcaemi

hypo

31

causes of hypocalcaemia

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

32

which causes are assoc with a raised PO4 (hypo)

CKD, hypoparathyroidism, pseudo, vit D deficiency, hypomagnesaemia

33

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

osteomalacia, acute pancreatitis, over hydration, respiratory alkalosis

34

when are the clinical features apparent in hyper and hypo

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

35

clinical features hypocalcaemia

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

what are the signs in hypocalcaemia

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

what is choreoathetosis

involuntary movements

38

treatment of hypocalcaemia

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

what can hypoparathyroidism be due to

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

40

treat hypoparathyroidism

calcitriol and thiazides

41

what is pseudohypoparathyroidism

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

42

what features do you get in pseudohypo

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

43

what happens in hypomagnesaemia

parasthesiae, ataxia, seizures, tetany, arrhythmias,

44

causes of hypomagnesaemia

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

45

what happens in hypermagneseamia

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

46

causes of hypermagnesaemia

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