Table 1: Vitamin D sterols currently available as medical treatments in nephrology field.

Nutritional vitamin DVDRA
Hydroxylation required to activate VDRHydroxylation required to activate VDR

Vitamin D2  
and its analogs
   Ergocalciferol25-hydroxylation and 1-hydroxylationParicalcitol
Doxercalciferol 1a(OH)D225-hydroxylation

Vitamin D3
and its analogs
Cholecalciferol25-hydroxylation and 1-hydroxylationAlfacalcidol 1a(OH)D325-hydroxylation
Calcifediol1-hydroxylationOxacalcitriol 22oxa1,25(OH)2D2

Note: all the VDRA reported in the table are considered analogs with the only exception of calcitriol, which corresponds to the natural form of 1,25(OH)2D3.
LVDRA: vitamin D receptor activators; VDR: vitamin D receptor.