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MET2 > Calcium > Flashcards

Calcium Flashcards

1
Q

Is acute low or high serum calcium more dangerous

A

Low

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2
Q

Are endocrine mechanisms for preventing hypocalcemia or hypercalcemia stronger

A

Hypocalcemia

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3
Q

dietary sources of calcium

A

Dairy products

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4
Q

How does calcium enter the circulation

A

dietary sources, or occasionally an IV infusion

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5
Q

Where is calcium stored

A

skeleton

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6
Q

How is calcium removed

A

via kidneys

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7
Q

Where is calcium stored

A

Skeleton

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8
Q

What percentage of skeletal calcium is interchangeable with free extracellular calcium

A

1%

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9
Q

What forms can calcium be in in the body

A

Protein bound
Ionised
Complexed

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10
Q

What proteins is some calcium bound to

A

Albumin
Globulin

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11
Q

What is the biologically active form of calcium

A

Ionised calcium

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12
Q

When does ionised calcium level change when total body calcium stays the same

A

Acid base status change

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13
Q

Why does serum ionised calcium decrease in alkalosis

A

Ca2+ binds to same site on albumin as H+ so more calcium is bound

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14
Q

What symptoms is felt when serum calcium falls

A

Lip tingling

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15
Q

Roles of calcium in the body

A

Muscle contraction
Neurotransmitter
Hormone release
Maintaining electrochemical gradient across cell membrane

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16
Q

What can low serum calcium lead to

A

Tachyarrhythmia
Tetany

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17
Q

How does hypocalcemia cause tachyarrhythmia and tetany

A

Ca stabilises voltage gated na channels
Hypocalcemia Increases permeability of excitable membranes in nerves and muscles to Na+, reducing threshold for action potential firing

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18
Q

What form is almost all serum calcium in

A

Ionised

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19
Q

Responding to low serum calcium is the primary role of which gland

A

Parathyroid

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20
Q

How does the parathyroid hormone increase serum calcium

A

Mobilises calcium form bone
Reduces calcium lost at kidneys
Increases proportion of dietary calcium absorbed via activation of vitamin D

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21
Q

What other ion is released when calcium is released from bone

A

Phosphate

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22
Q

Why does parathyroid hormone cause phosphate loss in urine

A

Allow excretion of phosphate released from bones with calcium

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23
Q

What cell types make up the parathyroid gland

A

Chief cells
Oxyphil cells

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24
Q

What do chief cells secrete in the parathyroid

A

Parathyroid hormone

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25
Q

What imaging is used to assess parathyroid pathologies

A

Technetium sestamibi scintigraphy

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26
Q

How long is the half life of PTH in circulation

A

2 mins

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27
Q

What is the major stimulus for PTH secretion

A

Fall in conc of serum ionised calcium

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28
Q

Where are calcium sensing receptors which detect low serum calcium

A

Cell surface

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29
Q

How does magnesium impact PTH secretion

A

Small decrease - stimulate PTH release
Chronic severe decrease - blocks PTH secretion + causes cellular resistance to PTH

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30
Q

How can magnesium decrease cause hypocalcemia

A

Severe magnesium decrease blocks PTH secretion and causes tissue level PTH resistance

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31
Q

How does normal/high serum calcium affect PTH

A

Decreases PTH secretion
Breaks down stored PTH
suppresses transcription of PTH gene

32
Q

Familial hypocalciuric hypercalcemia

A

Condition caused by an inactivating mutation of the calcium sensing receptor in cells, resetting the normal range of serum calcium at a higher level with no significant clinical effects

33
Q

Cinacalcet

A

Drug - Allosteric modulator of calcium sensing receptor to decrease PTH

34
Q

What drug can be given to patients with hyperparathyroidism to decrease PTH secretion

A

Cinacalcet

35
Q

Why does vitamin D deficiency elevate PTH levels

A

Vitamin D suppresses PTH transcription

36
Q

How does PTH affect bones

A

Increases calcium and phosphate resorption

37
Q

How does PTH affect intestines

A

Increases calcium and phosphate absorption

38
Q

How does PTH affect kidneys

A

Decreases calcium excretion and increases phosphate excretion

39
Q

Where in the kidney tubule is calcium reabsorbed

A

Proximal tubule and loop of henle

40
Q

What are the 2 routes of calcium reabsorption in the kidney

A

Paracellular route
Trans cellular route

41
Q

What drives calcium reabsorption in the kidney

A

Voltage gradient across cells

42
Q

How do loop diuretics decrease calcium reabsorption

A

Impair voltage gradient across tubule cells by binding to NAK2Cl channels in loop of henle

43
Q

How does PTH increase kidney calcium reabsorption

A

Upregulates channels and transporters - TRPV calcium channels, calcium ATPase, Na/Ca exchanger

44
Q

How do loop diuretics affect serum calcium level

A

Decrease

45
Q

How do thiazide diuretics affect serum calcium level

A

Increase

46
Q

Why does PTH Downregulate NaPi transporters

A

Reduce phosphate reabsorption

47
Q

Why does PTH upregulates 1 alpha hydroxylase

A

To activate vitamin D

48
Q

How does PTH effect Na H2O and HCO3 resorption

A

Inhibits

49
Q

How does PTH effect glucose metabolism

A

Causes proximal tubule Gluconeogenesis

50
Q

How does PTH activate osteoclasts

A

Increases RANK ligand production
Decreases OPG production

51
Q

What are the main constituents of bone

A

Collagen
Hydroxyapatite

52
Q

What is the main effect of vitamin D on bone

A

Provides calcium from gut to facilitate mineralisation

53
Q

What type of molecule is vitamin D

A

Hormone - not a vitamin

54
Q

Where is basic vitamin D converted to 25(OH)D

A

Liver

55
Q

Which enzyme is needed to convert 25OH)D3 to the calcitriol

A

1 alpha hydroxylase

56
Q

Why does kidney damage cause hypocalcemia

A

Decr calcium absorbtion from food due to Lack of activated vitamin D as kidney produces 1 alpha hydroxylase

57
Q

Where are vitamin D receptors

A

Mostly on nucleus
Some on cell membrane

58
Q

How does activation of the vitamin D receptor cause negative feedback

A

Inhibits 1 alpha hydroxylase preventing production of more activated vitamin D

59
Q

When does activation of the vitamin D receptor cause positive feedback and serum hypercalcemia

A

In macrophages fighting granulomatous disease eg TB

60
Q

Calcitriol

A

Active form of vitamin D

61
Q

What is the major role of calcitriol

A

Increase gut absorption of calcium and phosphate

62
Q

How does vitamin D deficiency affect bones

A

Impairs remineralisation making bones soft

63
Q

What conditions are caused by vitamin D deficiency in adults and children

A

Children - rickets
Adults - osteomalacia

64
Q

What causes osteoporosis

A

Long term elevated PTH release

65
Q

Which hormone is the most important in phosphate level regulation

A

FGF23

66
Q

How does low phosphate affect bones

A

Impairs bone mineralisation

67
Q

What can cause osteomalacia

A

Vitamin D deficiency
Low serum phosphate

68
Q

What type of mutation causes familial rickets

A

FGF23 actuvating Mutation

69
Q

What marker is released when thyroid C cells become neoplasticism in medullary thyroid cancer

A

Calcitonin

70
Q

What causes hypercalcemia of malignancy

A

PTH-related peptide paraneoplastic release from cancers

71
Q

What can hypercalcemia cause

A

Constipation
Depression
Kidney stones
Nephrogenic diabetes insipidus

72
Q

Main cause of hypocalcemia

A

Hypoparathyroidism

73
Q

Causes of hypoparathyroidism

A

Removal of glands in neck surgery
Autoimmune conditions
Genetic conditions
Severe vitamin D deficiency
Chronic kidney disease - decr activated vit D

74
Q

Causes of hypercalcemia

A

Hyperparathyroidism
Malignancy

75
Q

What causes primary hyperparathyroidism

A

Parathyroid tumour releasing excess PTH

76
Q

What causes secondary hyperparathyroidism

A

Natural response to low calcium or vit d deficiency

77
Q

What causes tertiary hyperparathyroidism

A

Parathyroid hyperplasia, usually due to CKD
Autonomous PTH production following secondary hyperparathyroidism

MET2 (25 decks)

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