23,25-Dihydroxyvitamin D₃ is liberated as a major vitamin D₃ metabolite in human urine after treatment with β-glucuronidase: Quantitative comparison with 24,25-dihydroxyvitamin D₃ by LC/MS/MS.

The complete understanding of the excretion of surplus 25-hydroxyvitamin D₃ [25(OH)D₃] in humans remains to be accomplished. In our previous study, 24,25-dihydroxyvitamin D₃ [24,25(OH)₂D₃] 24-glucuronide was identified as a major urinary vitamin D₃ metabolite, while the glucuronide of 23,25-dihydroxyvitamin D₃ [23,25(OH)₂D₃] is another metabolite of interest but has not been sufficiently evaluated. Although the quantitative analysis of 24,25(OH)₂D₃ liberated in urine by the treatment with β-glucuronidase (GUS) has been conducted, no information was provided about the amount of the glucuronidated 23,25(OH)₂D₃ in the urine.