ENND: Vitamins

Question 1

Diseases by vit D deficiency (3)

Answer 1

1. Rickets
2. Osteomalacia
3. Hypocalcemic tetany

Question 2

Cod liver oil protects against

Answer 2

Rickets

Question 3

Radiation wavelength for vit D synthesis

Answer 3

290-315 nm

UVB Radiation

Question 4

Major source of vit D synthesis

Answer 4

Endogenous production from precursor 7dehydrocholesterol

Question 5

Vit D3 other name

Answer 5

Cholecalciferol

Question 6

Sites of vit D hydroxylation and enzymes

Answer 6

1. Liver: makes 25-OH cholecalciferol (25-OH D3)

By cyp 27A1 (25 hydroxylases)

2. Kidney: 24,25 and 1,25 dihydroxy cholecalciferol

Question 7

Factors regulating vitD synthesis

Answer 7

1. S. Ca2+
   
   • Hypocalcemia increases PTH
   • PTH activates 1 alpha hydroxylase
2. S. Phosphate
   
   • Hypophasphatemia DIRECTLY activates 1AH
3. Feedback
   
   • Increased vitD inhibits 1AH