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Last reviewed dd mmm yyyy. Last edited dd mmm yyyy
Calcitriol (also called 1,25-dihydroxyvitamin D3), is the active form of D3
1,25-Dihydroxycholecalciferol, calcitriol, is therefore the product of liver and renal hydroxylation of vitamin D3, and is the most active metabolite of vitamin D.
It stimulates calcium uptake by the small intestine and this indirectly promotes mineralization of new bone.
Production of this active form of vitamin D is controlled by parathyroid hormone - PTH - and by serum phosphate concentration: a rise in PTH or a fall in serum phosphate increases 1,25-dihydrocholecalciferol synthesis.
1,25-Dihydroxycholecalciferol also facilitates renal reabsorption of calcium, and increases osteoclastic activity in bone.