Development of analysis of vitamin D metabolites

Vitamin D (D) plays important roles for homeostasis of serum calcium and so on, in human after metabolic activation. The measurements of concentrations of D metabolites in biological fluids are important for clinical and nutritional diagnoses. In these respects, developments of analysis of D metabolites, especially the phase I reaction products (free metabolites), have been carried out. In the first part of this report, the advancein developments of analysis of the free metabolites is reviewed according to the methodology over the last five years. The phase II reaction products (conjugated metabolites) of D, which are poorly understood compared to the free metabolites, are recently found in many kinds of animals, and much interest is focused on their physiological roles. In the second part, an overview of the identification and quantification of the conjugated D metabolites in biological fluids is presented mainly from our studies.