Calcium metabolism

Question 1

what effect does PTH have on Ca2+ and PO4

Answer 1

incr ca and decr po4

Question 2

how does PTH affect calcium

Answer 2

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

Question 3

when is PTH released

Answer 3

in hypocalcaemia and hyperphosphataemia

Question 4

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

Answer 4

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

Question 5

what is the normal value of calcium

Answer 5

2.2-2.6mmol/L

Question 6

what are the 3 main causes of hypercalcaemia

Answer 6

cancer, chronic renal failure, primary hyperparathyroidism

Question 7

what is the action of Mg

Answer 7

causes hypocalcaemia as prevents PTH release

Question 8

what do the labs measure for calcium

Answer 8

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

Question 9

what are the clinical features of hypercalcaemia

Answer 9

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

Question 10

what happens on the ECG in hypercalcaemia

Answer 10

decr QT interval

Question 11

what are the rarer causes of hypercalcaemia

Answer 11

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

Question 12

investigations hypercalcaemia

Answer 12

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

Question 13

where is vitamin D first hydroxylated and to what

Answer 13

liver- to 25-hydroxyl vit D

Question 14

where is 1,25 hydroxyl vit D made

Answer 14

kidneys

Question 15

how can you distinguish between malignancy and 1ary hyperparathyroidism

Answer 15

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

Question 16

what does an incr PTH indicate

Answer 16

hyperparathyroidism

Question 17

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

Answer 17

dehydration

Question 18

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

Answer 18

1ary or 3ary hyperparathyroidism

Question 19

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

Answer 19

raised ALP- bone mets, sarcoidosis, thyrotoxicosis, lithium

Question 20

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

Answer 20

myeloma, sarcoidosis, vit D excess

Question 21

how to treat acute hypercalcaemia

Answer 21

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

Question 22

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

Answer 22

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

Question 23

what cancers are commonly assoc with tumour induced hypercalcaemia

Answer 23

lung, breast, renal, myeloma

Question 24

biochem tumour induced hypercalcaemia

Answer 24

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

Question 25

what happens in chronic renal failure (hyper)

Answer 25

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

Question 26

what do the parathyroid glands secrete

Answer 26

1,84 PTH

Question 27

what happens to calcium and PO4 in primary hyperparathyroidism

Answer 27

ca incr, po4 incr- inappropriate

Question 28

what happens to calcium and PO4 in secondary hyperparathyroidism

Answer 28

ca decr, po4 incr- appropriate

Question 29

what happens to calcium and PO4 in tertiary hyperparathyroidism

Answer 29

after prolonged hypocalcaemia in secondary, get hypercalcaemia mimicking primary.

Question 30

which is less common hyper or hypocalcaemi

Answer 30

hypo

Question 31

causes of hypocalcaemia

Answer 31

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

Question 32

which causes are assoc with a raised PO4 (hypo)

Answer 32

CKD, hypoparathyroidism, pseudo, vit D deficiency, hypomagnesaemia

Question 33

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

Answer 33

osteomalacia, acute pancreatitis, over hydration, respiratory alkalosis

Question 34

when are the clinical features apparent in hyper and hypo

Answer 34

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

Question 35

clinical features hypocalcaemia

Answer 35

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

Question 36

what are the signs in hypocalcaemia

Answer 36

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

Question 37

what is choreoathetosis

Answer 37

involuntary movements

Question 38

treatment of hypocalcaemia

Answer 38

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

Question 39

what can hypoparathyroidism be due to

Answer 39

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

Question 40

treat hypoparathyroidism

Answer 40

calcitriol and thiazides

Question 41

what is pseudohypoparathyroidism

Answer 41

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

Question 42

what features do you get in pseudohypo

Answer 42

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

Question 43

what happens in hypomagnesaemia

Answer 43

parasthesiae, ataxia, seizures, tetany, arrhythmias,

Question 44

causes of hypomagnesaemia

Answer 44

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

Question 45

what happens in hypermagneseamia

Answer 45

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

Question 46

causes of hypermagnesaemia

Answer 46

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