Abstract
Measurement of 25-hydroxyvitamin D (25OH-vitD) is used to assess vitamin D status. We developed a high-sensitivity measurement method for 25OH-vitD and assessed the relationship between 250H-vitD and parathyroid hormone (PTH) in healthy adults. Aliquots (100 mu L) of serum were spiked with internal standard, proteins were precipitated, and samples were analyzed by liquid chromatography tandem mass spectrometry using 2-dimensional chromatographic separation. Total imprecision was less than 10%, and the limit of quantitation was 1.0 ng/mL. We determined the distribution of concentrations of 25OH-vitD(2) and 25OH-vitD(3) in healthy adults using samples collected during winter and summer and evaluated the association between 25OH-vitD and PTH. The difference between median concentrations of 250H-vitD in samples collected during winter and summer was 11 ng/mL (27 nmol/L). Statistically significant differences in concentrations of PTH were observed between groups of samples with 250H-vitD less than 11 (27 nmol/L) and 11 to 15 ng/mL (27-37 nmol/L) and between groups with 25 to 30 (62-75 nmol/L) and more than 40 ng/mL (100 nmol/L). Among the advantages of this method are its high sensitivity and specificity.