Assays On D3

This document discusses assays used to measure vitamin D and its metabolites in the body. It begins by providing background on vitamin D metabolism, with vitamin D obtained from sunlight or diet and undergoing hydroxylation in the liver and kidneys to become biologically active. Current assays measure circulating levels of vitamin D, 25-hydroxyvitamin D (25-OH-D), or 1,25-dihydroxyvitamin D (1,25(OH)2D). The 25-OH-D assay is most useful for determining overall vitamin D status as it reflects both dietary and sunlight exposure. Measurement of 1,25(OH)2D is useful for evaluating disorders in calcium metabolism related to errors in its production. Assays have advanced