vitamin D

                 (1)         (2)                   (3)
         7-DHC  ----->  D3  ----->  25-OH vit D3  ----->  1,25-OH vit D3

(1) skin

sunlight converts 7-dehydrocholesterol to vit D3 (cholecalciferol)

(2) liver

25-hydroxylation

(3) kidneys

1-hydroxylation to active form

requires parathyroid hormone (PTH)

• vit D promotes calcium absorption from bowel
• deficiency ==> rickets

© 2002, C.E. Kahn, Jr.
2002-04-18