Calcium Metabolism Flashcards
what do the parathyroid glands do when they sense low serum calcium?
increase PTH secretion
what effect does PTH have on the bones?
causes release of calcium and phosphorus
= increased serum calcium
what effect does PTH have on the kidneys?
increases calcitriol formation
increases calcium reabsorption
what does calcitriol do?
stimulates release of calcium from bone
increases absorption of dietary calcium
= increased serum calcium
what are the four key presentations of hypercalcaemia?
bone pain
kidney stones
abdominal pain
psychiatric disturbances
what are the four main symptoms of acute hypercalcaemia?
thirst
dehydration
confusion
polyuria
what are the two main causes of hypercalcaemia?
primary hyperparathyroidism
malignancy
what drugs can cause hypercalcaemia?
vitamin D
thiazide diuretics
what is the first line investigation to determine the cause of hypercalcaemia?
measure PTH
what are the three diagnostic criteria for primary hyperparathyroidism?
raised serum calcium
raised serum PTH
increased urine calcium excretion
what are the management options for primary hyperparathyroidism?
surgery
cinacalcet
what is cinacalcet?
a calcium mimetic
what are the indications for parathyroidectomy for primary hyperparathyroidism?
end organ damage
very high calcium
poor eGFR
what are calcium and PTH like in primary hyperparathyroidsm?
high calcium
high PTH
what are calcium and PTH like in secondary hyperparathyroidism?
low calcium
high PTH
what are calcium and PTH like in tertiary hyperparathyroidism?
high calcium
high PTH
how is hypocalciuric hypercalcaemia caused?
autosomal dominant inheritance
how does hypocalciuric hypercalcaemia present?
usually asymptomatic
what is seen on biochemistry of hypocalciuric hypercalcaemia?
mild hypercalcaemia
reduced urine calcium excretion
PTH may be slightly raised
what is seen on ECG in hypocalcaemia?
QT prolongation
what is involved in the long term management of hypocalcaemia?
calcium supplements
vitamin D
what does calcium release from cells depend on?
magnesium
what are calcium levels like in magnesium deficiency?
high
what causes pseudohypoparathyroidism?
genetic defect in GNAS 1
what is seen on bloods in pseudohypoparathyroidism?
low calcium
high PTH
what is seen on bloods in pseudo-pseudohypoparathyroidism?
normal
