title: Normalized vitamin D metabolite concentrations are better correlated to pharmacological effects than measured concentrations.
abstract: BACKGROUND
  Vitamin D deficiency has been associated with a multitude of diseases, ranging from fractures to cancer. Nearly 99% of vitamin D metabolites are bound to proteins, altering the relationship between concentration and activity.
  
  
  RESULTS
  Normalized concentrations were calculated and validated using published data regarding the correlation of 25-hydroxyvitamin D with bone mineral density. In addition, healthy and kidney disease subjects were recruited for preliminary investigations. Use of the normalizing equations resulted in statistically significant improvements in the relationship between vitamin D metabolites and several markers of health status.
  
  
  CONCLUSIONS
  Normalized concentrations are similar to clinically reported values and are easier to interpret than free or bioavailable concentrations, since their values match the range of measured total concentrations.
authors.affiliation: Department of Pharmacy Practice, Albany College of Pharmacy & Health Sciences, 106 New Scotland Avenue, Albany, NY 12208, USA; Division of Nephrology & Hypertension, Albany Medical College, 25 Hackett Boulevard, Albany, NY 12208, USA; Department of Pharmacy Practice, Albany College of Pharmacy & Health Sciences, 106 New Scotland Avenue, Albany, NY 12208, USA; Division of Nephrology & Hypertension, Albany Medical College, 25 Hackett Boulevard, Albany, NY 12208, USA.
authors.forename: Darius
authors.initials: D
authors.lastname: Mason
authors.affiliation: Department of Pharmaceutical Sciences, Albany College of Pharmacy & Health Sciences, 106 New Scotland Avenue, Albany, NY 12208, USA; Department of Pharmaceutical Sciences, Albany College of Pharmacy & Health Sciences, 106 New Scotland Avenue, Albany, NY 12208, USA.
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Donabella
authors.affiliation: Department of Pharmacy Practice, Albany College of Pharmacy & Health Sciences, 106 New Scotland Avenue, Albany, NY 12208, USA; Department of Pharmacy Practice, Albany College of Pharmacy & Health Sciences, 106 New Scotland Avenue, Albany, NY 12208, USA.
authors.forename: Daryl
authors.initials: D
authors.lastname: Nnani
authors.affiliation: Department of Pharmaceutical Sciences, Albany College of Pharmacy & Health Sciences, 106 New Scotland Avenue, Albany, NY 12208, USA; Department of Pharmaceutical Sciences, Albany College of Pharmacy & Health Sciences, 106 New Scotland Avenue, Albany, NY 12208, USA.
authors.forename: Florin Marcel
authors.initials: FM
authors.lastname: Musteata
keywords: 1,25-dihydroxyvitamin D; 25-hydroxyvitamin D; normalized concentrations; vitamin D binding protein; vitamin D metabolites