Abstract Methods for the measurement of vitamin D and its metabolites using stable isotope- labeled internal standards and mass spectrometry are reviewed. The synthesis of both labeled and unlabeled standards is illustrated, and details of the synthesis of (26, 26, 27, 27, 27-2 H 5)-25, 26-dihydroxyvitamin D 3 and (28, 28, 28-2 H 3)-24, 25-dihydroxyvitamin D 2 are given. The use of in vitro biologic systems for the production of further metabolites of ...
