Lecture #14 - Vitamin D

Question 1

What are the two main forms of vitamin D?

Answer 1

The two main forms are ergocalciferol (vitamin D2, found in plant foods) and cholecalciferol (vitamin D3, made in human skin with exposure to UVB light).

Question 2

Describe the metabolism of vitamin D in the body.

Answer 2

Vitamin D is metabolized in two steps:

first, it is converted to 25-hydroxyvitamin D (25-OHD3) in the liver.

Then, it is converted to its active form, calcitriol (1,25-OHD3), in the kidneys.

Question 3

How does vitamin D regulate calcium levels in the body?

Answer 3

Vitamin D increases calcium absorption in the intestines and, together with parathyroid hormone, regulates calcium resorption from bones, maintaining adequate serum calcium levels.