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
