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 concentration s of D metabolites in biological fluids are important for clinical and nutr itional diagnoses. In these respects, developments of analysis of D metabol ites, especially the phase I reaction products (free metabolites), have bee n carried out. In the first part of this report, the advancein developments of analysis of the free metabolites is reviewed according to the methodolo gy over the last five years. The phase II reaction products (conjugated met abolites) of D, which are poorly understood compared to the free metabolite s, are recently found in many kinds of animals, and much interest is focuse d on their physiological roles. In the second part, an overview of the iden tification and quantification of the conjugated D metabolites in biological fluids is presented mainly from our studies.