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dc.contributor.authorSollid, Stina Therese
dc.contributor.authorStrand Hutchinson, Moira
dc.contributor.authorBerg, Vivian
dc.contributor.authorFuskevåg, Ole-Martin
dc.contributor.authorFigenschau, Yngve Anton
dc.contributor.authorThorsby, Per Medbøe
dc.contributor.authorJorde, Rolf
dc.date.accessioned2017-03-10T13:18:43Z
dc.date.available2017-03-10T13:18:43Z
dc.date.issued2016-01-05
dc.description.abstractObjective:<br>To determine the relationship between serum total 25-hydroxyvitamin D (25(OH)D), directly measured free 25(OH)D and calculated free 25(OH)D with regard to vitamin D-binding protein (DBP) phenotypes, sex, BMI, age and season, and their interrelationship to vitamin D supplementation.<br>Design, patients and interventions:<br>A randomized controlled trial with 20 000 IU of vitamin D3 per week or placebo for 12 months was designed. A total of 472 subjects, 236 in each of the intervention groups, were included in the analyses.<br>Main outcome measures:<br>Baseline serum concentrations and increases in serum total 25(OH)D, directly measured free 25(OH)D, calculated free 25(OH)D and DBP.<br>Results:<br>Serum total 25(OH)D and DBP concentrations were significantly lower in subjects with the phenotype Gc2/Gc2 compared to phenotypes with the Gc1S allele, and lower in males compared to females. When using directly measured free 25(OH)D, the differences related to DBP phenotypes and sexes were clearly diminished. All calculated free 25(OH)D concentrations were overestimated compared to the directly measured free 25(OH)D. Serum parathyroid hormone showed an inverse correlation with all vitamin D parameters analyzed. The increases after 12 months of vitamin D supplementation were not significantly different for any of the vitamin D parameters regardless of DBP phenotype, sex or age. Supplementation with vitamin D did not affect serum DBP.<br>Conclusion:<br>Direct measurements of free 25(OH)D reduce the differences seen in total 25(OH)D between DBP phenotype groups and sexes, probably caused by differences in DBP concentrations. With conditions affecting serum DBP concentrations, direct measurements of free 25(OH)D should be considered.en_US
dc.description.sponsorshipThis study was supported by the Novo Nordisk foundation (grant number: R195-A16126), the North Norway Regional Health Authority (grant number: 6856/SFP1029-12), the Norwegian Diabetes Association, UiT The Arctic University of Norway and the Research Council of Norway (grant number: 184766)en_US
dc.descriptionSource: <a href=http://dx.doi.org/10.1530/EJE-15-1089>doi: 10.1530/EJE-15-1089</a>en_US
dc.identifier.citationSollid, St. et al. Effects of Vitamin D binDing protein phenotypes and Vitamin D supplementation on serum total 25(OH)D and directly measured free 25(OH)D. European Journal of Endocrinology. 2016;174(4):445-452en_US
dc.identifier.cristinIDFRIDAID 1367868
dc.identifier.doi10.1530/EJE-15-1089
dc.identifier.issn0804-4643
dc.identifier.issn1479-683X
dc.identifier.urihttps://hdl.handle.net/10037/10547
dc.language.isoengen_US
dc.publisherBioScientificaen_US
dc.relation.journalEuropean Journal of Endocrinology
dc.relation.projectIDinfo:eu-repo/grantAgreement/RCN/KLINISK/184766/Norway/Prevention of type 2 diabetes with vitamin D supplementation in subjects with reduced glucose tolerance detected in the Tromsø studyen_US
dc.rights.accessRightsopenAccessen_US
dc.subjectVDP::Medisinske Fag: 700::Klinisk medisinske fag: 750::Endokrinologi: 774en_US
dc.subjectVDP::Medical disciplines: 700::Clinical medical disciplines: 750::Endocrinology: 774en_US
dc.titleEffects of Vitamin D binding protein phenotypes and Vitamin D supplementation on serum total 25(OH)D and directly measured free 25(OH)Den_US
dc.typeJournal articleen_US
dc.typeTidsskriftartikkelen_US
dc.typePeer revieweden_US


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