Isotachysterol 3 is an impurity in the preparation of vitamin D3 .1 It stimulates intestinal calcium transport and bone calcium mobilization in control, as well as in anephric, rats fed a low-calcium and vitamin D-deficient diet when administered at a dose of 5 ?g/animal.2
1.Tartivita, K.A., Sciarello, J.P., and Rudy, B.C.High-performance liquid chromatographic analysis of vitamins I: Quantitation of cholecalciferol or ergocalciferol in presence of photochemical isomers of the provitamin and application to cholecalciferol resinsJ. Pharm. Sci.65(7)1024-1027(1976) 2.Holick, M.F., DeLuca, H.F., Kasten, P.M., et al.Isotachysterol3 and 25-hydroxyisotachysterol3: Analogs of 1,25-dihydroxvitamin D3Science180(4089)964-966(1973)