Effect of vitamin D2 and vitamin D3 on the serum concentrations of 1,25(OH)2D2, and 1,25(OH)2D3 in normal subjects

Abstract

Serum concentrations of vitamin D₂ and vitamin D₃ metabolites were measured in 19 normal subjects before and during treatment with either vitamin D₂ or vitamin D₃, 4000 IU per day for 8 weeks. Vitamin D₂ treatment increased the serum concentration of 1,25(OH)₂D₂, but a corresponding decrease in 1,25(OH)₂D₃ resulted in an unchanged serum concentration of total 1,25(OH)₂D. During treatment with vitamin D₃, the serum concentration of 1,25(OH)₂D metabolites was unchanged. We conclude that the production of 1,25(OH)₂D is tightly regulated and that 1α-hydroxylase does not discriminate between D₂ and D₃ metabolites in normal subjects.