Basic and Clinical Concepts Related to Vitamin D Metabolism and Action

(Second of Two Parts) Assays for Vitamin D Metabolites The basic advances in our understanding of the metabolism and mechanism of action of vitamin D not only are important in physiology and nutrition but have been successfully applied to the study of the pathophysiology of a myriad of metabolic bone disorders. Initially, assay procedures were developed to measure vitamin D metabolites. Competitive protein binding is the most widely used method for the assay of vitamin D metabolites, and various selective binding proteins, such as plasma carriers and intracellular receptors, have been employed. These measurements have led to increased comprehension of.