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MET 2 > Calcium > Flashcards

Calcium Flashcards

1
Q

In which 2 ways can calcium be carried around in the body

A

Ionised or unionised

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2
Q

What ion binds to albumin in the same way as calcium

A

Hydrogen

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3
Q

Describe the binding of hydrogen/ calcium in acidosis

A

Increased ionised calcium as less binding to albumin

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4
Q

Describe the binding of hydrogen/ calcium in alkalosis

A

Decreased in ionised calcium because more bound to albumin

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5
Q

Why do some people experience tinging in their lips and extremities when they hyperventilate

A

Reduction in ionised calcium- symptoms of hypocalciumia

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6
Q

2 main roles of calcium

A

Structural role

Intracellular signalling

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7
Q

Is calcium higher inside or outside the cell

A

Outside

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8
Q

Which channels are responsible for firing of action potential

A

Fast sodium channels

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9
Q

What happens if you reduce calcium in the blood

A

Nerves are more likely to fire- tachyarrythmias, fibrillation, cardiac arrest

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10
Q

What does calcium do the fast sodium channels

A

Stabilises them

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11
Q

What % of body phosphate is mineralised in the bone

A

85%

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12
Q

What is released by parathyroid gland

A

Parathyroid hormone

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13
Q

What type of hormone is PTH

A

Peptide hormone

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14
Q

What are the pharyngeal arches made of

A

Bone and cartilage

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15
Q

What 2 cell types are present in the parathyroid

A

Oxyphilic and chief cells

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16
Q

Which cells release PTH

A

Chief cells in the parathyroid gland

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17
Q

When do oxyphil cells appear

A

Puberty

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18
Q

Describe the order that different organs process parathyroid hormone in

A

Rough ER–> golgi–> vesicles

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19
Q

What is the biggest trigger to PTH released

A

Low levels of serum calcium

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20
Q

What is represented by the maximal secretory rate of PTH

A

Parathyroid reserve

Capacity to repsond to hypocalcaemia

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21
Q

What receptor senses low levels of calcium

A

Calcium sensing receptor

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22
Q

What kind of receptor is the calcium sensing receptor

A

G protein coupled receptor

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23
Q

What happens if calcium sensing receptor is activated

A
  • Reduces PTH secretion
  • Increases breakdown of stored PTH
  • Suppresses transcription of PTH gene
  • Blocks stimulation of cAMP
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24
Q

Other than calcium, what else activates calcium sensing receptor

A

Magnesium, certain amino acids

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25
Q

Other than calcium, what else may determine PTH secretion

A

Activated vitamin D (calcitriol) suppresses PTH

Phosphate stimulates

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26
Q

What is the action of PTH in the kidney

A

Decreases calcium excretion

Increases phosphate excretion

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27
Q

What is the action of PTH on bone

A

Increases calcium and phosphate resorption

28
Q

What is the action of PTH in the intestine

A

Increases absorption of calcium and phosphate

Some evidence for direct effects but mainly indirectly through calcitriol

29
Q

How much calcium resorption occurs in the proximal tubule

A

65%

30
Q

What drives calcium resorption in the proximal tubule

A

Voltage gradient

31
Q

How much resorption occurs in the loop of Henle

A

20%

32
Q

What inhibits calcium resorption in the loop of Henle

A

Loop diuretics

33
Q

What % of calcium is absorbed in the distal tubule

A

10%

34
Q

Which area of the kidney is PTH dependent in terms of calcium resorption

A

Distal tubule

35
Q

What calcium channels are found in the distal tubule

A

TRPV calcium channels

36
Q

What is the action of PTH in the distal tubule

A

Upregulate:

  • TRPV calcium channels
  • Calcium ATPase channels
  • Na/Ca exchanger
37
Q

What does PTH downregulate in the kidney, and what is the effect of this

A
  • Downregulation of NaPi transporters= reduced phosphate reabsorption
38
Q

PTH stimulates gluconeogenesis in which area of the kidney

A

Proximal tubule

39
Q

PTH inhibits the reabsorption of what in the kidney

A

Sodium, water, bicarbonate

40
Q

What is the effect of PTH and calcitriol on the bone

A
  • Stimulate RANKL production, signalling for bone resorption

- Downregulation of osteoprotegerin

41
Q

What is the relationship beween bone resorption and formation

A

They are equal

42
Q

What is the relationship between bone remodelling and formation in menopausal women

A

Resorption> formation

43
Q

What is the effect of PTH on IGFI and IL 1

A

Increases

44
Q

What is the effect of glucocorticoids on bone remodelling

A
  • Reduce osteoblast numbers

- Increase RANKL

45
Q

What is the effect of oestrogen on bone remodelling

A

Inhibiits bone remodelling

46
Q

What are some radiological signs of primary hyperparathyroidism

A

Terminal tuft erosion
Rugger jersey spine
Brown tumour
Subperiosteal erosion

47
Q

What kind of receptor is the vitamin D receptor

A

Nuclear and membrane bound

48
Q

What is the effect of vitamin D in the bone

A
  • Reduces type 1 collagen expression
  • Increases osteocalcin and RANKL
  • Facilitates osteoclast differentiation
49
Q

What is the effect of vitamin D on phosphate

A
  • Increases gut absorption

- Increases levels of GFG23 to remove it via renal excretion

50
Q

What is the effect of vitamin D on cellular proliferation

A

Reduces it

51
Q

What is the effect of vitamin D on amino acid uptake

A

Deficiency–> myopathy

52
Q

What is FGF 23

A

A phosphatonin- a hormone that reduces serum phosphate levels

53
Q

What happens if there is an activating mutation if FGF23

A

Autosomal dominant hypophosphataemic rickets

54
Q

What do you call a tumour induced osteomalacia

A

Paraneoplastic FGF23

55
Q

What may happen if there are low levels GFG23

A

Familial tumoral calcinosis

56
Q

Where is calcitonin released from

A

Thyroid C cells

57
Q

What is primary hyperparathyroidism

A

Absence of hypocalcaemia

May be caused by parathyroid adenoma, carcinoma, hyperplasia

58
Q

What does primary hyperparathyroidism lead to

A

Hypercalcaemia

59
Q

What is secondary hyperparathyroidism

A

Compensation for hypocalcaemia

60
Q

When should asymptomatic primary hyperparathyroidism be treated

A 
Low BMD
Renal calculi
Renal impairment
Calcium >3.0
Age <50
61
Q

What scan should be used to localise an adenoma

A

MIBI scan

62
Q

What happens in hypocalcaemia

A

Convulsion
Arrythmia
Tetany
Paraesthesia

63
Q

What can lead to hypocalcaemia

A

Chronic kidney disease

Vit D deficiency

64
Q

How is hypoparathyroidism treated acutely

A

IV or oral calcium supplement

65
Q

How is hypoparathyroidism treated chronically

A

VIt D orally

66
Q

What is familial hypocalciuric hypercalcaemia

A

Inactivating mutations of CaSR

  • parathyroid can’t sense high calcium
  • PTH not suppressed by high calcium
  • CaSR in kidney not activated
  • PTH-calcium curve shifts to the right
67
Q

What serum results would be seen in familial hypocalciuris hypercalcaemia

A

High serum Ca
Low urine Ca
High serum Mg

MET 2 (32 decks)

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