Calcium metabolism Flashcards
briefly describe regulation of calcium
CaSR on parathyroid gland sense low serum calcium
PTH secretion
Acts on bone to induce bone resorption
Increases calcium reabs and reduces PO4 reabsorption
Increased production of 1,25-hydroxy vitamin D f
Increases Calcium and phosphate absorption from intestine
Levels restored
relationship between PTH and calcium
low calcium= high PTH
what is require for PTH secretion
Magnesium
what affects calcium
albumin conc
pH
how does albumin affect Ca
if albumin is low, total measured calcium is low, however less is bound so calcium levels remain normal.
how does pH affect calcium
If there are more hydrogen ions they bind to albumin and displace calcium and vice versa
pH goes down, ionised calcium goes up
pH goes up, ionised calcium goes down
what are the 2 main causes of hypercalcaemia
primary hyperparathyroidism
malignancy
what test do you always do to confirm primary hyperparathyroidism
urine test
clinical features of multiple myeloma
Calcium is high
Renal impairment
Anaemia
Bone pain
how does sarcoidosis cause hypercalcaemia
Sarcoidsosis- small tumour like masses comprised of inflame cells and fibrous tissues, around these granulomas there are cells that produce ACE
Ca is high in granulomatous disease because gran have macrophages which contain mora alpha-hydroxylase so more 1,25-hydroxyvitamin D production
pathogenesis of familial hypocalcinuric hypercalcaemia
Mutation in CaSR in parathyroid gland and kidneys. Parathyroid gland won’t switch off, reabsorption of all calcium in the kidney, leading to low calcium in the urine.
causes of hypercalcaemia
malignancy primary hyperparathyroidism thyrotoxicosis thiazides sarcoidosis FHH lithium therapy TB immobilisation
causes of hypomagnesaemia
malabsorption PPIs malnutrition chronic alcoholism cirrhosis loop diuretics
consequences of hypoMg
hypoCa
HypoK
