title: A simplified assay for dihydroxylated vitamin D metabolites in human serum: application to hyper- and hypovitaminosis D.
abstract: We describe a simplified assay for 24,25-and 1.25-dihydroxyvitamin D in human serum. It involves two preparative steps, and normal chick intestine is used in preparing cytosol-binding protein. Our results for 24,25-dihydroxyvitamin D include a reference interval of 2.9--16 nmol/L (1.2--6.7 microgram/L), a mean of 6.7 nmol/L (2.8 microgram/L), an intra-assay CV of 11%, and an interassay CV of 22%. For 1,25-dihydroxyvitamin D, these data were 29--168 pmol/L (12--70 ng/L), 86 pmol/L (36 ng/L), 12%, and 22%, respectively. In hypoparathyroid patients with vitamin D intoxication, mean concentrations of 25-hydroxyvitamin D and 24,25-dihydroxyvitamin D in serum were significantly above normal; the 1,25-dihydroxyvitamin D concentrations were significantly below normal. Patients with malabsorption and/or post-gastrectomy states had significantly subnormal values for both 25-hydroxyvitamin D and 24,25-dihydroxyvitamin D in serum, and there was a significantly negative correlation between each of these biochemical values and the severity of osteomalacia. We also discuss cost effectiveness of assaying vitamin D metabolites in human serum.
mesh_terms: D000328:Adult; D000818:Animals; D001681:Biological Assay; D002352:Carrier Proteins / Q000378:metabolism; D002645:Chickens; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D004100:Dihydroxycholecalciferols / Q000097:blood*; D005743:Gastrectomy; D006801:Humans; D006887:Hydroxycholecalciferols / Q000097:blood*; D007011:Hypoparathyroidism / Q000097:blood; D008286:Malabsorption Syndromes / Q000097:blood; D008875:Middle Aged; D009392:Nephrectomy; D010018:Osteomalacia / Q000097:blood; D012016:Reference Values; D012756:Sheep; D014808:Vitamin D Deficiency / Q000378:metabolism; D014809:Vitamin D-Binding Protein
chemical_list: D002352:Carrier Proteins; D004100:Dihydroxycholecalciferols; D006887:Hydroxycholecalciferols; D014809:Vitamin D-Binding Protein