Question

Vitamin D is formed in the skin and hydroxylated in two places before it is in its active form. Where does the second hydroxylation occur

a) Liver
b) Kidneys
c) Lungs
d) Intestines

Answer 1

Vitamin D is hydroxylated in two places before it is in its active form. The second hydroxylation occurs in the kidneys.

Step-by-step explanation:

The second hydroxylation of vitamin D occurs in the kidneys. In the kidneys, vitamin D is transformed into 1,25(OH)D₂ (calcitriol), a biologically active form of vitamin D. The first hydroxylation of vitamin D occurs in the liver, where it turns into 25(OH)D (calcidiol), the primary form of circulating vitamin D.