Flashcards in Calcium metabolism Deck (46):
what effect does PTH have on Ca2+ and PO4
incr ca and decr po4
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.
when is PTH released
in hypocalcaemia and hyperphosphataemia
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.
what is the normal value of calcium
what are the 3 main causes of hypercalcaemia
cancer, chronic renal failure, primary hyperparathyroidism
what is the action of Mg
causes hypocalcaemia as prevents PTH release
what do the labs measure for calcium
total plasma Ca2+- 40% bound to albumin and the rest free ionised calcium
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.
what happens on the ECG in hypercalcaemia
decr QT interval
what are the rarer causes of hypercalcaemia
immobilisation, thyrotoxicosis, vit D toxicity, lithium, sarcoidosis, hypoadrenalism
bone profile- ca, po4, albumin, ALP. FBC, ESR, liver profile, renal profile, TFTs, X rays. PTH and 25 (OH)D
where is vitamin D first hydroxylated and to what
liver- to 25-hydroxyl vit D
where is 1,25 hydroxyl vit D made
how can you distinguish between malignancy and 1ary hyperparathyroidism
decr albumin in malignancy along with decr Cl-, alkalosis, decr K+, incr PO4, incr ALP.
what does an incr PTH indicate
if albumin is high and urea is raised what is the cause of the hypercalcaemia
if the albumin is normal or low and phosphate is decr or normal what is the cause (hyper)
1ary or 3ary hyperparathyroidism
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
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
how to treat acute hypercalcaemia
dehydration- IV 0.9% saline; bisphosphonates- zoledronic acid, sodium clodronate, ibandronic acid; chemo; steroids
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
what cancers are commonly assoc with tumour induced hypercalcaemia
lung, breast, renal, myeloma
biochem tumour induced hypercalcaemia
suppressed PTH, hypoalbuminaemia, incr ESR, treat IV bisphosphonates, treat tumour
what happens in chronic renal failure (hyper)
decr GFR. tertiary hyperparathyroidism. vit D metabolites (iatrogenic)/ parathyroidectomy if very high.
what do the parathyroid glands secrete
what happens to calcium and PO4 in primary hyperparathyroidism
ca incr, po4 incr- inappropriate
what happens to calcium and PO4 in secondary hyperparathyroidism
ca decr, po4 incr- appropriate
what happens to calcium and PO4 in tertiary hyperparathyroidism
after prolonged hypocalcaemia in secondary, get hypercalcaemia mimicking primary.
which is less common hyper or hypocalcaemi
causes of hypocalcaemia
hypoparathyroidism, pseudoparathyroidism, vit D deficiency, Mg deficiency, malabsorption, renal failure
which causes are assoc with a raised PO4 (hypo)
CKD, hypoparathyroidism, pseudo, vit D deficiency, hypomagnesaemia
which causes are assoc with a normal or decr PO4 (hypo)
osteomalacia, acute pancreatitis, over hydration, respiratory alkalosis
when are the clinical features apparent in hyper and hypo
hyper >3 mmol/L. hypo 2 mmol/L
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
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
what is choreoathetosis
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
what can hypoparathyroidism be due to
auto immune or post thyroid surgery. PTH low. PO4 high creatinine normal.
calcitriol and thiazides
what is pseudohypoparathyroidism
rare inherited condition. defect in the PTH receptor with PTH resistance. incr PTH decr Ca incr PO4.
what features do you get in pseudohypo
short stature, shortened metacarpals. intellectual disability and treat with calcitriol.
what happens in hypomagnesaemia
parasthesiae, ataxia, seizures, tetany, arrhythmias,
causes of hypomagnesaemia
diuretics, diarrhoea, ketoacidosis, alcohol, decr Ca, decr K, decr PO4. treat with Mg salts eg MgSO4
what happens in hypermagneseamia
neuromusc depression, decr bp and pulse, hyporeflexia, CNS and resp depression, coma.