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

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Flashcards in LMP301 Lecture 11: Calcium, Vit D, Parathyroid Deck (90)
1

Where is calcium excreted?

- intestines (poop)
- kidneys

2

Which hormones regulate calcium homeostatsis?

- parathyroid hormone
- 1,25 (OH)2 vit D
- calcitonin

3

What stimulates PTH release?

low Ca++

4

effect of PTH on bone

reabsorption (break down)

5

effect of PTH on kidney

- Ca++ reabsorption
- P secretion
- incr. 1-OH'ase
- incr. 1,25 (OH)2 vit D

6

Where does PTH act on?

- bones
- kidneys

7

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

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

8

Where can 25-OH'ase be found?

liver

9

where can 1a-OH'ase be found?

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

10

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

1,24,25-(OH)3D3

11

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

24,25-(OH)2D3
24-OH'ase

12

Sources of vit D3

- supplement
- sunlight on skin
- milk
- salmon

13

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

regulate cell growth (prevent cancer)

Prevent autoimmune diseases

14

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

prevent autoimmune diseases

maintain calcium homoeostasis (muscle & bone health)

15

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

- intestines
- bones
- parathyroid gland

16

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

- increase Ca absorption
- incr P absorption

17

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

raise blood Ca++ levels

18

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

increase reabsoprtion

19

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

decrease PTH

20

Feedback of 1,25-(OH)2D3

- inhibit its own synthesis
- promotes its own breakdown

21

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

vit D binding protein

22

receptor for 1,25-(OH)2D3

nuclear vit D receptor

23

calcitonin is secreted by...

parafollicular / C cells of thyroid gland

24

Secretion of calcitonin is stimulated by...

- high Ca
- GI hormones

25

Effect of calcitonin

- lower serum CA
- lower serum P
- stops bone reabsorption

26

Calcitonin is used as treatment for which bone diseases?

- post-menopausal osteoporosis
- Paget's disease

27

Calcitonin is a tumour marker for...

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

28

Tetany is a symptom of...

hypocalcemia

29

Tetany

flexed wrist & ankle joint, muscle twitching, cramps

30

Hypocalcemia is usually present with...

neuromuscular hyperexcitability (tetany, Trousseau's sign)

31

Hypercalcemia is usually present with...

reduced neuromuscular excitability (fatigue, weakness, depression)

32

Hypercalcemia may induce...

ADH resistance = nephrogenic diabetes
- thirst
- polydipsia
- polyuria

33

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

kidney stones

34

causes of hypocalcemia

- hypoparathyroidism
- pseudohypoparathyroidism
- magnesium deficiency
- renal failure
- vit D deficiency

35

hypoparathyroidism

parathyroid can't produce PTH

36

pseudohypoparathyroidism

high PTH
low Ca++

PTH resistance

37

magnesium deficiency contributing to hypocalcemia

Mg affects secretion of PTH
(high Mg = more PTH secretion)

38

Why might renal failure cause hypocalcemia

- Retain P, so Ca++ is secreted
- 1,25-(OH)2D3 deficiency

39

causes of vit D deficiency

- diet
- lack of sun
- can't absorb
- chronic liver disease
- chronic renal disease
- vit D dependent rickets

40

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

- low Ca
- (in response) high PTH
This is secondary hypoparathyrodism

41

What are the causes of secondary hyperpaarathyrodism?

- renal failure
- vit D deficiency

42

3 ways which hypercalcemia may happen

1. intestine absorption
2. bone reabsorption
3. renal reabsorption

43

Causes of hypercalcemia

- problem at parathyroid gland
- malignancies
- milk-alkali syndrome
- increased 1-OH'ase activity
- FHH

44

FHH

familial hypocalciuric hypercalcemia
- mutations of calcium sensing receptor in parathyroid gland
- autosomal dominant
- not severe, asymptomatic

45

FHH can be mistakenly diagnosed as...

hyperparathyroidism

46

Some cancers that may cause hypercalcemia may secrete...

PTHrP (related protein)

47

milk-alkali syndrome

take too much antacid
- increase bicarb / Ca++
- metabolic alkalosis

48

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

Sarcoidosis

49

> 60% of patients with primary hyperparathyrodism are...

post-menopausal women

50

Biochemical profile of primary hyperparathyrodism

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

51

Difference between PTH and PTHrP

PTH on chrom 11
PTHrP on chrom 12

52

Similarities between PTH and PTHrP

first 8 AA on N term shows close homology

53

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

PTH receptor
Mimic PTH effects

54

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

Very common
Breast milk

55

biochemical differences of PTH and PTHrP

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

56

PTHrP is produced in...

some tumours that cause humoral hypercalcemia of malignancy (HHM)

57

Common bone disorders

- osteomalacia & rickets
- paget's disease
- osteoporosis

58

is Ca++ a marker of bone disease?

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

59

What is responsible for bone resorption? formation?

osteoclasts
osteoblasts

60

Markers for bone resorption

deoxypyridinoline

61

deoxypyridinoline

collagen degradation product

62

markers for bone formation

- alkaline phosphatase
- osteocalcin

63

alkaline phosphatase

bone specific isoenzyme

64

osteocalcin

produced by osteoblasts

65

Rickets

defects of bone & cartilage mineralization in children

66

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

Osteomalacia
Rickets

67

Osteomalacia

defective bone mineralization in adults

68

difference between Osteomalacia and Rickets

- adult vs. child
- cartilage also impacted in children
- same disease but different names for diff age

69

causes of rickets

vit D deficiency

70

Rickets is divided into...

- vit D dependent type I
- vit D dependent type II

71

vit D dependent type I

- hereditory
- defective 1-OH'ase
- can't make 1,25(OH)2D3

72

Treatment for vit D dependent type I

give 1,25(OH)2D3

73

biochemical profile of vit D dependent type I

- high PTH
- low Ca++
- low 1,25(OH)2D

74

biochemical profile of vit D dependent type II

- high 1,25(OH)2D

75

vit D dependent type II rickets

vit D receptor defect

76

Paget's disease

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

77

clincal presentation of paget's diease

severe bone pain
- loss of hearing (bones in ear)

78

biochemical profile of Paget's disease

- normal Ca
- increased alkaline phosphatase activity

79

treatment of Paget's disease

- bisphosphate drug
- calcitonin

80

relationship between calcitonin and osteoclasts

calcitonin can stop osteoclast activity

81

Who is more affected by osteoporosis? This is called...

post-menopausal women
- primary osteoporosis

82

cause of primary osteoporosis?

unknown

83

cause of secondary osteoporosis?

Increased cortisol -> increased osteoclast activity

84

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

1. exercise
2. weight bearing (gravity, standing)

85

What are the 3 major forms of vit D supplements?

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

86

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

native

(Ca++ metabolites can be used if more severe)

87

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

25(OH)D

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

88

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

1,25(OH)2D

89

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

1,25(OH)2D

90

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

Nothing; insensitivity to vit D