Calcium homeostasis Flashcards
What is the receptor in the parathyroid gland that senses calcium levels?
calcium sensing receptor
What is cholecalciferol converted to in the liver?
25 OH vitamin D
Where does 25 OH vit D get converted to 1,25 OH vit D?
kidneys
What are the actions of vitamin D?
acts on the intestines to increase absorption of calcium and phosphate; increases osteoclastic activity in the bones; acts on the kidneys to increase reabsorption
What are the symptoms of acute hypercalcaemia?
thirst; dehydration; confusion; polyuria
What are the chronic symptoms of hypercalcaemia?
myopathy; osteopaenia; fractures; depression; HT; abdo pain- pancreatitis; ulcers; renal stones
What are the causes of hypercalaemia?
primary hyperparathyroidism; malignancy; drugs; granulomatous disease; familia hypocalciuric hypercalcaemia; high turnover
What is seen on biochemistry of primary hyperparathyroidism?
raised serum calcium; raised serum PTH; increased urin calcium excretion
What are the mechanisms associated with hypercalcaemia of malignancy?
metastatic bone destruction; PTHrp from solid tumours; osteoclast activating factors
What is the treatment for acute hypercalcaemia?
fluids- saline; loop diuretics once rehydrated; bisphosponates; steorid (sarcoid)
What drugs can cause hypercalcaemia?
thiazides; vit D
What is the treatment for primary hyperparathyroidism?
surgery
When is a parathyroidectomy indicated?
end organ damage; very high calcium; under 50 yo; eGFR <60mL/min
What is primary hyperparathyroidism?
primary overactivity of parathyroid eg adenoma
what is secondary hyperparathyroidism?
physiological response to low calcium
What is tertiary hyperparathyroidism?
parathyroid becomes autonomous after many years of secondary
What are the actions of PTH?
increasing osteoclastic activity releasing calcium and phosphate from bones; increasing calcium and decreasing phosphate reabsorption in the kidney; active vit D production is increased; overall :increased calcium and decreased phosphate
What are the test resulats in primary hyperparathyroidism?
increased calcium and PTH; decreased phosphate; increased alk phos; urinary calcium increased
What is the action of cinacalet?
increases sensitivity of parathyroid cells to calcium (decreasing PTH secreion)
what are the causes of secondary hyperparathyroidism?
decreased vit D uptake; chronic renal failure
What cancers produce PTHrP?
squamous lung cancers; breast and renal cell carcinomas
Why is PTH decreased in malignat hyperparathyroidism?
PTHrP is not detected in assay and increased calcium is switching off PTH release
What causes primary hypoparathyroidism?
gland failure
What are the causes of primary hypoparathyroidism?
AI; congenital- DiGeorge
What are the causes of secondary hypoparathyroidism?
radiation; surgery; hypomagnesaemia
What is pseudohypoparathyroidism?
failure of target cell response to PTH
What are the signs of pseudohypoparathyroidism?
short metacarpals; round face; short staure; calcified basal gaglia; decreased IQ
What is pseudopseudohypoparathyroidism?
has the features of pseudohypoparathyroidism but with normal biochemistry
What causes both pseudo and pseudopseudo hypoprathyroidism
genetic mutation
What causes familial hypocalciuric hypercalcaemia?
A mutation in the calcium sensing receptor leading to general calcium hyposensitivity- in parathyroid and kidneys
What is the best way to differentiate between FFH and primary hyperparathyroidism?
they have different renal processing of calcium
What are the symproms of hypocalcaemia?
parasthesia; muscle cramps; tetany; muscle weakness; fatiuge; bronchospasm or laryngospasm; fits; Chovsteks sign; Trousseau
What is seen on ECG with hypocalcaemia?
QT prolongation
What are the causes of hypocalcaemia?
hypoparathyroidism; vitD deficiency; chronic renal failure; pancreatitis; hyperventialiation
What is the treatment for acute hypocalcaemia?
IV clacium gluconate
What is the long term managment for hypocalcaemia?
calcium supplement; vit D
What happens in hypomagnesaemia
calcium release from cells is dependent on magnesium; in deficiency, intracellular calcium is high; PTH release is inihbited- secondary hypoparathyroidism
What are the causes of hypomagnesaemia?
alcohol; drugs- thiazide; PPI; GI illness; pancreatitis; malabsoprtion
What are teh actions of vitamin D?
increased caclium and phosphate absorption; hibition of PTH release; enhanced bone turnover; increaased calcium and phosphate absorption from the kidneys
What are the biochemical results with osteomalacia?
low calcium; low phosphate; high alk phos; low vit D high PTH
What are the long term consequences of vitamine D deficieny?
malignancy esp. colon; heart disease; DM
