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dc.contributor.advisorJorde, Rolf
dc.contributor.authorJohnsen, Martin Solvang
dc.date.accessioned2016-10-26T08:24:42Z
dc.date.available2016-10-26T08:24:42Z
dc.date.issued2015-10-29
dc.description.abstractIntroduction/background In the circulation 25-hydroxyvitamin D (25(OH)D) is bound to vitamin D-binding protein (DBP) and albumin. Only a small fraction is in the unbound, free form. According to the ‘free-hormone-hypothesis’ only the free form is biologically active. Genetic differences in DBP may affect the binding to 25(OH)D and thereby the amount of free 25(OH)D. Methods In the present study sera were obtained from 265 postmenopausal women with low bone mass density (BMD). Serum 25(OH)D, DBP and albumin were measured and the free and bio-available (free + albumin-bound) 25(OH)D calculated. Based on genotyping of the polymorphisms rs7041 and rs4588, the six common DBP phenotypes were identified and the free and bio-available 25(OH)D calculated according to the corresponding binding coefficients. Relations between measures of 25(OH)D and PTH and BMD were evaluated with linear regression adjusted for age and BMI. Results The calculated amount of free and bio-available 25(OH)D was 0.03% and 13.1%, respectively, of the measured total serum 25(OH)D. Adjusting for DBP phenotype affected the calculated free and bio-available 25(OH)D levels up to 37.5%. All measures of 25(OH)D correlated significantly with PTH, whereas a significant association with BMD was only seen for the free and bio-available 25(OH)D measures. Adjusting for the DBP phenotypes improved the associations. These relations were almost exclusively seen in subjects not using vitamin D and/or calcium supplements. Conclusion The free and bio-available forms of 25(OH)D may be a more informative measure of vitamin D status than total 25(OH)D. Adjustment for DBP phenotype may improve this further.en_US
dc.identifier.urihttps://hdl.handle.net/10037/9895
dc.language.isoengen_US
dc.publisherUiT Norges arktiske universiteten_US
dc.publisherUiT The Arctic University of Norwayen_US
dc.rights.accessRightsopenAccessen_US
dc.rights.holderCopyright 2015 The Author(s)
dc.subject.courseIDMED-3910
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.subjectVitamin Den_US
dc.subjectSNPen_US
dc.subjectFree 25(OH)Den_US
dc.subjectBioavailable 25(OH)Den_US
dc.subjectDBPen_US
dc.titleSerum free and bio-available 25-hydroxyvitamin D correlate better with bone density than serum total 25-hydroxyvitamin Den_US
dc.typeMaster thesisen_US
dc.typeMastergradsoppgaveen_US


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