Determination of mono- and dihydroxy-vitamin D metabolites in normal subjects and patients with different calcium metabolic diseases.

Reliable assays to determine the vitamin D metabolites are useful aids in the study of disorders involving vitamin D metabolism, and in the evaluation of the response in patients receiving vitamin D treatment. We report here the establishment in our laboratory of a method capable of measuring 25(OH)D, (including 25(OH)D2 and 25(OH)D3), 1,25(OH)2D and 24,25(OH)2D in a single blood sample. The method involves methanol/dichloromethane extraction and Sephadex LH-20 chromatography. The monhydroxylated fraction was purified on Lipidex 5000 and separated in 25(OH)D2 and 25(OH)D3 on high pressure liquid chromatography (HPLC), followed by ultra violet absorbance (UV) detection. The dihydroxylated fraction was separated by HPLC and quantified by protein-binding assays. The method is precise and accurate. The vitamin D metabolites were measured in different groups of patients and in normal subjects.