Calcitriol (
INN), also called
1,25-dihydroxycholecalciferol or
1,25-dihydroxyvitamin D3, is the hormonally active metabolite of
vitamin D with three
hydroxyl groups (abbreviated
1,25-(OH)2D3 or simply
1,25(OH)2D), It was first identified by
Michael F. Holick in work published in 1971. Calcitriol increases the level of
calcium (Ca
2+) in the
blood by increasing the uptake of calcium from the
gut into the blood, and possibly increasing the release of calcium into the blood from
bone.