Calcitriol

Biologically active form of vitamin D3 in calcium absorption and deposition. 1α,25-Dihydroxyvitamin D3 has widespread effects on cellular differentiation and proliferation, and can modulate immune responsiveness, and central nervous system function. Recent studies suggest that 1α,25-dihydroxyvitamin D3 acts as a chemopreventive agent against several malignancies including cancers of the prostate and colon and shows synergy with other anticancer compounds. Cholecalciferol is an inactive form of vitamin D3 which undergoes various levels of hydroxylation to form active vitamin D3 analogs. 1α-Hydroxyvitamin D3 (alfacalcidol is a synthetic analog that is metabolized to 1,25-dihydroxycholecalciferol, the biologically active form of vitamin D3 in calcium absorption and deposition. 1α,25-Dihydroxyvitamin D3 has widespread effects on cellular differentiation and proliferation, and can modulate immune responsiveness, and central nervous system function. Recent studies suggest that 1α,25-dihydroxyvitamin D3 acts as a chemopreventive agent against several malignancies including cancers of the prostate and colon and shows synergy with other anticancer compounds.

1. Holick, MF; Schnoes, HK; Deluca, HF; Suda, T; Cousins, RJ (1971). "Isolation and identification of 1,25-dihydroxycholecalciferol. A metabolite of vitamin D active in intestine". Biochemistry. 10 (14): 2799–804. doi:10.1021/bi00790a023. PMID 4326883.
2. Norman AW, Myrtle JF, Midgett RJ, Nowicki HG, Williams V, Popják G (July 1971). "1,25-dihydroxycholecalciferol: identification of the proposed active form of vitamin D3 in the intestine". Science. 173 (3991): 51–4. doi:10.1126/science.173.3991.51. PMID 4325863.