Which form is the active form of vitamin D?

Which form is the active form of vitamin D?

• A. Inactive: 25(OH) D3
• B. Active: 1,25(OH) D3
• C. Inactive: 1,25(OH) D3
• D. Active: 25(OH) D3

Answer: (B)

Active vitamin D is the dihydroxylated form: 1,25-dihydroxyvitamin D3 (calcitriol). The body first converts vitamin D to 25-hydroxyvitamin D3 in the liver, and then the kidney adds another hydroxyl group to form the active hormone. This active metabolite binds the vitamin D receptor and regulates genes that increase calcium and phosphate absorption from the gut and support bone mineralization. The storage form, 25-hydroxyvitamin D3, is the major circulating form used to assess vitamin D status but is not active by itself. Therefore, the active form is 1,25-dihydroxyvitamin D3.

Active vitamin D is the dihydroxylated form: 1,25-dihydroxyvitamin D3 (calcitriol). The body first converts vitamin D to 25-hydroxyvitamin D3 in the liver, and then the kidney adds another hydroxyl group to form the active hormone. This active metabolite binds the vitamin D receptor and regulates genes that increase calcium and phosphate absorption from the gut and support bone mineralization. The storage form, 25-hydroxyvitamin D3, is the major circulating form used to assess vitamin D status but is not active by itself. Therefore, the active form is 1,25-dihydroxyvitamin D3.