Calcium and vit D and bones

Question 1

What is drop in calcium sensed by

Answer 1

alcium sensitive receptor on cell surface of renal tubules and PTH cell in neck

Question 2

Effect of PTH release when low calcium

Answer 2

PTH receptors on renal tubules and bones - activaton of vit D -> intersitial Ca absorption
Within 3-5 mintues of low calcium
Hours - bone reabsorption and release of Ca

Question 3

Synthesis of vit D to acitvate

Answer 3

Skin → Vit D3 hydroxylated in liver to calcidiol → Hydroxylated in kidneys → calcitriol

D3 = colecalciferol

Question 4

Sources of vit D

Answer 4

90% from sunlight UV-B
Colcalciferol - oily fish, egg yolks, meat
Ergocalciferol from yeast/mushrooms

Question 5

Markers of bone resorption (osteoclast activity

Answer 5

C-terminal telopeptide type 1 collagen (CTX)
NTX
Hydroxyproline

Question 6

Bone formation markers

Answer 6

• ALP - bone specific
• Osteocalcin
• N-terminal propeptide of type U procollagen (P1NP)

Question 7

T score vs Z score

Answer 7

• Z-score
  
  • BMD compared to age matched population
• T-score:
  
  • BMD vs race and sex matched to peak adult BMD