Calcium homeostasis Flashcards

1
Q

What is the receptor in the parathyroid gland that senses calcium levels?

A

calcium sensing receptor

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2
Q

What is cholecalciferol converted to in the liver?

A

25 OH vitamin D

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3
Q

Where does 25 OH vit D get converted to 1,25 OH vit D?

A

kidneys

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4
Q

What are the actions of vitamin D?

A

acts on the intestines to increase absorption of calcium and phosphate; increases osteoclastic activity in the bones; acts on the kidneys to increase reabsorption

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5
Q

What are the symptoms of acute hypercalcaemia?

A

thirst; dehydration; confusion; polyuria

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6
Q

What are the chronic symptoms of hypercalcaemia?

A

myopathy; osteopaenia; fractures; depression; HT; abdo pain- pancreatitis; ulcers; renal stones

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7
Q

What are the causes of hypercalaemia?

A

primary hyperparathyroidism; malignancy; drugs; granulomatous disease; familia hypocalciuric hypercalcaemia; high turnover

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8
Q

What is seen on biochemistry of primary hyperparathyroidism?

A

raised serum calcium; raised serum PTH; increased urin calcium excretion

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9
Q

What are the mechanisms associated with hypercalcaemia of malignancy?

A

metastatic bone destruction; PTHrp from solid tumours; osteoclast activating factors

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10
Q

What is the treatment for acute hypercalcaemia?

A

fluids- saline; loop diuretics once rehydrated; bisphosponates; steorid (sarcoid)

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11
Q

What drugs can cause hypercalcaemia?

A

thiazides; vit D

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12
Q

What is the treatment for primary hyperparathyroidism?

A

surgery

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13
Q

When is a parathyroidectomy indicated?

A

end organ damage; very high calcium; under 50 yo; eGFR <60mL/min

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14
Q

What is primary hyperparathyroidism?

A

primary overactivity of parathyroid eg adenoma

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15
Q

what is secondary hyperparathyroidism?

A

physiological response to low calcium

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16
Q

What is tertiary hyperparathyroidism?

A

parathyroid becomes autonomous after many years of secondary

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17
Q

What are the actions of PTH?

A

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

18
Q

What are the test resulats in primary hyperparathyroidism?

A

increased calcium and PTH; decreased phosphate; increased alk phos; urinary calcium increased

19
Q

What is the action of cinacalet?

A

increases sensitivity of parathyroid cells to calcium (decreasing PTH secreion)

20
Q

what are the causes of secondary hyperparathyroidism?

A

decreased vit D uptake; chronic renal failure

21
Q

What cancers produce PTHrP?

A

squamous lung cancers; breast and renal cell carcinomas

22
Q

Why is PTH decreased in malignat hyperparathyroidism?

A

PTHrP is not detected in assay and increased calcium is switching off PTH release

23
Q

What causes primary hypoparathyroidism?

A

gland failure

24
Q

What are the causes of primary hypoparathyroidism?

A

AI; congenital- DiGeorge

25
Q

What are the causes of secondary hypoparathyroidism?

A

radiation; surgery; hypomagnesaemia

26
Q

What is pseudohypoparathyroidism?

A

failure of target cell response to PTH

27
Q

What are the signs of pseudohypoparathyroidism?

A

short metacarpals; round face; short staure; calcified basal gaglia; decreased IQ

28
Q

What is pseudopseudohypoparathyroidism?

A

has the features of pseudohypoparathyroidism but with normal biochemistry

29
Q

What causes both pseudo and pseudopseudo hypoprathyroidism

A

genetic mutation

30
Q

What causes familial hypocalciuric hypercalcaemia?

A

A mutation in the calcium sensing receptor leading to general calcium hyposensitivity- in parathyroid and kidneys

31
Q

What is the best way to differentiate between FFH and primary hyperparathyroidism?

A

they have different renal processing of calcium

32
Q

What are the symproms of hypocalcaemia?

A

parasthesia; muscle cramps; tetany; muscle weakness; fatiuge; bronchospasm or laryngospasm; fits; Chovsteks sign; Trousseau

33
Q

What is seen on ECG with hypocalcaemia?

A

QT prolongation

34
Q

What are the causes of hypocalcaemia?

A

hypoparathyroidism; vitD deficiency; chronic renal failure; pancreatitis; hyperventialiation

35
Q

What is the treatment for acute hypocalcaemia?

A

IV clacium gluconate

36
Q

What is the long term managment for hypocalcaemia?

A

calcium supplement; vit D

37
Q

What happens in hypomagnesaemia

A

calcium release from cells is dependent on magnesium; in deficiency, intracellular calcium is high; PTH release is inihbited- secondary hypoparathyroidism

38
Q

What are the causes of hypomagnesaemia?

A

alcohol; drugs- thiazide; PPI; GI illness; pancreatitis; malabsoprtion

39
Q

What are teh actions of vitamin D?

A

increased caclium and phosphate absorption; hibition of PTH release; enhanced bone turnover; increaased calcium and phosphate absorption from the kidneys

40
Q

What are the biochemical results with osteomalacia?

A

low calcium; low phosphate; high alk phos; low vit D high PTH

41
Q

What are the long term consequences of vitamine D deficieny?

A

malignancy esp. colon; heart disease; DM