Medical Isotopes specializes in labeled vitamins that are used in medical research as internal standards and other analytical applications. Vitamins have diverse biochemical functions. Some have hormone-like functions as regulators of mineral metabolism (such as vitamin D), or regulators of cell and tissue growth and differentiation (such as some forms of vitamin A). Others function as antioxidants (e.g., vitamin E and sometimes vitamin C). The largest number of vitamins (such as B complex vitamins) function as precursors for enzyme cofactors, that help enzymes in their work as catalysts in metabolism. Some of Medical Isotopes’ most requested vitamins are 25-Hydroxy Vitamin D3-d6, 25-Dihydroxy Vitamin D2-d6 and Vitamin E-5,7,8-d9.