Vitamin D

Question 1

Source

Answer 1

D2 from ingested plants
D3 from sun exposure in skin

Both converted to 25-OH in liver
and to 1,25 in kidney

Question 2

Inactive form

Answer 2

24,25-(OH)2-D3

Question 3

Function

Answer 3

1) increase abs of dietary Ca2+ and phos

2) increase bone resob of Ca2+ and phos

Question 4

Regulation

Answer 4

Stimulated by

1) high PTH,
2) low Ca2+
3) low Phos

1,25-(OH)2 feedback inhibits its own production

Question 5

Deficiency

Answer 5

Rickets in kids

Osteomalacia in adults

Question 6

PTH vs. 1,25

Answer 6

PTH: leads to Ca2+ reabs and low phos reabs in the kidney

1,25: leads to increased abs of both Ca2+ and phos in gut.