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LMP301 > LMP301 Lecture 11: Calcium, Vit D, Parathyroid > Flashcards

LMP301 Lecture 11: Calcium, Vit D, Parathyroid Flashcards

Calcium, Vit D, parathyroid

1
Q

Where is calcium excreted?

A
  • intestines (poop)

- kidneys

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2
Q

Which hormones regulate calcium homeostatsis?

A
  • parathyroid hormone
  • 1,25 (OH)2 vit D
  • calcitonin
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3
Q

What stimulates PTH release?

A

low Ca++

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4
Q

effect of PTH on bone

A

reabsorption (break down)

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5
Q

effect of PTH on kidney

A
  • Ca++ reabsorption
  • P secretion
  • incr. 1-OH’ase
  • incr. 1,25 (OH)2 vit D
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6
Q

Where does PTH act on?

A
  • bones

- kidneys

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7
Q

How do we get to the active form of 1,25 (OH)2 vit D?

A
  1. pro-vitamin D –(UV)–> vit D
  2. vit D –(25-OH’ase)–> 25-(OH)D3
  3. 25-(OH)D3 –(1a-OH’ase)–> 1,25-(OH)2D3
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8
Q

Where can 25-OH’ase be found?

A

liver

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9
Q

where can 1a-OH’ase be found?

A

many tissues, including kidneys, pancreas, colon, prostate, breasts…

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10
Q

The active 1,25 (OH)2 vit D can be converted into the inactive…

A

1,24,25-(OH)3D3

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11
Q

25 OH vit D can be converted into ____ by ____ (not the reaction to make 1,25-(OH)2D3)

A

24,25-(OH)2D3

24-OH’ase

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12
Q

Sources of vit D3

A
  • supplement
  • sunlight on skin
  • milk
  • salmon
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13
Q

function of 1,25-(OH)2D3 at pancreas, colon, prostate, breasts…

A

regulate cell growth (prevent cancer)

Prevent autoimmune diseases

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14
Q

function of 1,25-(OH)2D3 at kidneys

A

prevent autoimmune diseases

maintain calcium homoeostasis (muscle & bone health)

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15
Q

Where does 1,25-(OH)2D3 act on?

A
  • intestines
  • bones
  • parathyroid gland
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16
Q

effect of 1,25-(OH)2D3 on intestines

A
  • increase Ca absorption

- incr P absorption

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17
Q

Overall effect of 1,25-(OH)2D3

A

raise blood Ca++ levels

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18
Q

effect of 1,25-(OH)2D3 on bone

A

increase reabsoprtion

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19
Q

effect of 1,25-(OH)2D3 on parathyroid gland

A

decrease PTH

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20
Q

Feedback of 1,25-(OH)2D3

A
  • inhibit its own synthesis

- promotes its own breakdown

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21
Q

1,25-(OH)2D3 is bound to ___ when in circulation

A

vit D binding protein

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22
Q

receptor for 1,25-(OH)2D3

A

nuclear vit D receptor

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23
Q

calcitonin is secreted by…

A

parafollicular / C cells of thyroid gland

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24
Q

Secretion of calcitonin is stimulated by…

A
  • high Ca

- GI hormones

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25
Q

Effect of calcitonin

A
  • lower serum CA
  • lower serum P
  • stops bone reabsorption
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26
Q

Calcitonin is used as treatment for which bone diseases?

A
  • post-menopausal osteoporosis

- Paget’s disease

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27
Q

Calcitonin is a tumour marker for…

A

medullary thyroid carcinoma (tumor of the C cells in thyroid gland)

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28
Q

Tetany is a symptom of…

A

hypocalcemia

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29
Q

Tetany

A

flexed wrist & ankle joint, muscle twitching, cramps

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30
Q

Hypocalcemia is usually present with…

A

neuromuscular hyperexcitability (tetany, Trousseau’s sign)

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31
Q

Hypercalcemia is usually present with…

A

reduced neuromuscular excitability (fatigue, weakness, depression)

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32
Q

Hypercalcemia may induce…

A

ADH resistance = nephrogenic diabetes

  • thirst
  • polydipsia
  • polyuria
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33
Q

hypercalcemia may cause ___ because of hypercalciuria and Ca buildup in the kidney

A

kidney stones

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34
Q

causes of hypocalcemia

A
  • hypoparathyroidism
  • pseudohypoparathyroidism
  • magnesium deficiency
  • renal failure
  • vit D deficiency
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35
Q

hypoparathyroidism

A

parathyroid can’t produce PTH

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36
Q

pseudohypoparathyroidism

A

high PTH
low Ca++

PTH resistance

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37
Q

magnesium deficiency contributing to hypocalcemia

A

Mg affects secretion of PTH

high Mg = more PTH secretion

38
Q

Why might renal failure cause hypocalcemia

A
  • Retain P, so Ca++ is secreted

- 1,25-(OH)2D3 deficiency

39
Q

causes of vit D deficiency

A
  • diet
  • lack of sun
  • can’t absorb
  • chronic liver disease
  • chronic renal disease
  • vit D dependent rickets
40
Q

what are the Ca and PTH levels in renal failure and vit D deficiency?

A
  • low Ca
  • (in response) high PTH
    This is secondary hypoparathyrodism
41
Q

What are the causes of secondary hyperpaarathyrodism?

A
  • renal failure

- vit D deficiency

42
Q

3 ways which hypercalcemia may happen

A
  1. intestine absorption
  2. bone reabsorption
  3. renal reabsorption
43
Q

Causes of hypercalcemia

A
  • problem at parathyroid gland
  • malignancies
  • milk-alkali syndrome
  • increased 1-OH’ase activity
  • FHH
44
Q

FHH

A

familial hypocalciuric hypercalcemia

  • mutations of calcium sensing receptor in parathyroid gland
  • autosomal dominant
  • not severe, asymptomatic
45
Q

FHH can be mistakenly diagnosed as…

A

hyperparathyroidism

46
Q

Some cancers that may cause hypercalcemia may secrete…

A

PTHrP (related protein)

47
Q

milk-alkali syndrome

A

take too much antacid

  • increase bicarb / Ca++
  • metabolic alkalosis
48
Q

Example of a disease with increased 1-OH’ase activity

A

Sarcoidosis

49
Q

> 60% of patients with primary hyperparathyrodism are…

A

post-menopausal women

50
Q

Biochemical profile of primary hyperparathyrodism

A
  • high PTH
  • high Ca
  • low P
  • high / normal 1,25-(OH)2D3
51
Q

Difference between PTH and PTHrP

A

PTH on chrom 11

PTHrP on chrom 12

52
Q

Similarities between PTH and PTHrP

A

first 8 AA on N term shows close homology

53
Q

Where does PTHrP bind, and what effects does it have?

A

PTH receptor

Mimic PTH effects

54
Q

Is PTHrP common? Where can high concentrations of it usually be found?

A

Very common

Breast milk

55
Q

biochemical differences of PTH and PTHrP

A

PTH cause slight increase of 1,25-(OH)2D3

PTHrP cause slight decrease of 1,25-(OH)2D3

56
Q

PTHrP is produced in…

A

some tumours that cause humoral hypercalcemia of malignancy (HHM)

57
Q

Common bone disorders

A
  • osteomalacia & rickets
  • paget’s disease
  • osteoporosis
58
Q

is Ca++ a marker of bone disease?

A

Not necessarily; bone disease can occur even when Ca++ is normal

59
Q

What is responsible for bone resorption? formation?

A

osteoclasts

osteoblasts

60
Q

Markers for bone resorption

A

deoxypyridinoline

61
Q

deoxypyridinoline

A

collagen degradation product

62
Q

markers for bone formation

A
  • alkaline phosphatase

- osteocalcin

63
Q

alkaline phosphatase

A

bone specific isoenzyme

64
Q

osteocalcin

A

produced by osteoblasts

65
Q

Rickets

A

defects of bone & cartilage mineralization in children

66
Q

What are the two bone diseases present in adults/children?

A

Osteomalacia

Rickets

67
Q

Osteomalacia

A

defective bone mineralization in adults

68
Q

difference between Osteomalacia and Rickets

A
  • adult vs. child
  • cartilage also impacted in children
  • same disease but different names for diff age
69
Q

causes of rickets

A

vit D deficiency

70
Q

Rickets is divided into…

A
  • vit D dependent type I

- vit D dependent type II

71
Q

vit D dependent type I

A
  • hereditory
  • defective 1-OH’ase
  • can’t make 1,25(OH)2D3
72
Q

Treatment for vit D dependent type I

A

give 1,25(OH)2D3

73
Q

biochemical profile of vit D dependent type I

A
  • high PTH
  • low Ca++
  • low 1,25(OH)2D
74
Q

biochemical profile of vit D dependent type II

A
  • high 1,25(OH)2D
75
Q

vit D dependent type II rickets

A

vit D receptor defect

76
Q

Paget’s disease

A
  • increased osteoclast activity

- increased osteoblast activity, but new bone is not formed properly

77
Q

clincal presentation of paget’s diease

A

severe bone pain

- loss of hearing (bones in ear)

78
Q

biochemical profile of Paget’s disease

A
  • normal Ca

- increased alkaline phosphatase activity

79
Q

treatment of Paget’s disease

A
  • bisphosphate drug

- calcitonin

80
Q

relationship between calcitonin and osteoclasts

A

calcitonin can stop osteoclast activity

81
Q

Who is more affected by osteoporosis? This is called…

A

post-menopausal women

- primary osteoporosis

82
Q

cause of primary osteoporosis?

A

unknown

83
Q

cause of secondary osteoporosis?

A

Increased cortisol -> increased osteoclast activity

84
Q

To maintain proper bone health, what 2 requirements must be met?

A
  1. exercise

2. weight bearing (gravity, standing)

85
Q

What are the 3 major forms of vit D supplements?

A
  1. native vit D
  2. 25(OH)D
  3. 1,25(OH)2D
86
Q

vit D deficiency caused by malnutrition / lack of sun / only breastfed baby should be treated by which form of vit D?

A

native

Ca++ metabolites can be used if more severe

87
Q

vit D deficiency caused by chronic liver disease should be treated by which form of vit D?

A

25(OH)D

1,25(OH)2D can also be used if severe

88
Q

vit D deficiency caused by chronic renal disease should be treated by which form of vit D?

A

1,25(OH)2D

89
Q

vit D deficiency caused by vit D dependent rickets type I should be treated by which form of vit D?

A

1,25(OH)2D

90
Q

vit D deficiency caused by vit D dependent rickets type II should be treated by which form of vit D?

A

Nothing; insensitivity to vit D

LMP301 (18 decks)

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