1β,25-Dihydroxyvitamin D3: A new vitamin D metabolite in human serum

We present evidence for the widespread presence of 1β,25(OH)2D3, a new vitamin D metabolite, in human serum. The level increases with rising serum 25(OH)D concentrations and is particularly high in patients with very high 25(OH)D levels. We previously demonstrated that 1β,25(OH)2D3 is a poor genomic agonist but a potent non-genomic antagonist of 1α,25(OH)2D3. The clinical implications of the presence of this analog therefore require further exploration.