title: The role of serum total and free 25-hydroxyvitamin D and PTH values in defining vitamin D status at the end of winter: a representative survey.
abstract: We sought the lowest serum total 25-hydroxyvitamin D (t-25OHD) values in geographic areas with four seasons and investigated whether the calculation of serum free 25-hydroxyvitamin D (f-25OHD) could provide additional information on vitamin D status. This is a representative, cross-sectional study restricted to a sampling period at the end of winter, using a non-probability, stratified sample of the adult community-dwelling Hungarian population (n = 882). We measured t-25OHD, vitamin D binding protein (DBP), parathyroid hormone (PTH), and albumin levels. f-25OHD concentrations were calculated. We assessed environmental factors that could affect vitamin D levels and diseases possibly related to vitamin D deficiency. Mean t-25OHD values of the total population were 41.3 ± 20.6 nmol/L. t-25OHD levels were below 75, 50, and 30 nmol/L in 97, 77, and 34 % of participants not receiving vitamin D supplementation, respectively. t-25OHD values weakly positively correlated with DBP (r = 0.174; p = 0.000), strongly with f-25OHD (r = 0.70; p = 0.000). The association between t-25OHD and f-25OHD and between t-25OHD and PTH were non-linear (psquared term= 0.0004 and 0.004, respectively). t-25OHD levels were not affected by gender, age, place of residence; however, they were related to body mass index, sunbed sessions, and tropical travel. In contrast, f-25OHD levels were different in males and females but were not related to obesity. t- and f-25OHD were lower among people with cardiovascular diseases (p = 0.012). Nearly the entire Hungarian population is vitamin D insufficient at the end of winter. The use of t-25OHD could show a spurious association with obesity; however, it does not reflect the obvious sex difference.
authors.affiliation: 1st Department of Medicine, Semmelweis University Faculty of Medicine, Budapest, Korányi Sándor u. 2/a, Budapest, 1083, Hungary.
authors.forename: Boglárka
authors.initials: B
authors.lastname: Szabó
authors.affiliation: Department of Epidemiology and Public Health, University College London, London, UK.
authors.forename: Ádám G
authors.initials: ÁG
authors.lastname: Tabák
authors.affiliation: Faculty of Health Science, Institute of Diagnostics, University of Pécs, Pécs, Hungary.|Central Laboratory, Markusovszky Teaching Hospital, Szombathely, Hungary.
authors.forename: Erzsébet
authors.initials: E
authors.lastname: Toldy
authors.affiliation: National Institute of Rheumatology and Physiotherapy, Budapest, Hungary.
authors.forename: László
authors.initials: L
authors.lastname: Szekeres
authors.affiliation: 1st Department of Medicine, Semmelweis University Faculty of Medicine, Budapest, Korányi Sándor u. 2/a, Budapest, 1083, Hungary.
authors.forename: Balázs
authors.initials: B
authors.lastname: Szili
authors.affiliation: 1st Department of Medicine, Semmelweis University Faculty of Medicine, Budapest, Korányi Sándor u. 2/a, Budapest, 1083, Hungary.
authors.forename: Bence
authors.initials: B
authors.lastname: Bakos
authors.affiliation: 1st Department of Medicine, Semmelweis University Faculty of Medicine, Budapest, Korányi Sándor u. 2/a, Budapest, 1083, Hungary.
authors.forename: Bernadett
authors.initials: B
authors.lastname: Balla
authors.affiliation: 1st Department of Medicine, Semmelweis University Faculty of Medicine, Budapest, Korányi Sándor u. 2/a, Budapest, 1083, Hungary.
authors.forename: János Pál
authors.initials: JP
authors.lastname: Kósa
authors.affiliation: 1st Department of Medicine, Semmelweis University Faculty of Medicine, Budapest, Korányi Sándor u. 2/a, Budapest, 1083, Hungary.
authors.forename: Péter
authors.initials: P
authors.lastname: Lakatos
authors.affiliation: 1st Department of Medicine, Semmelweis University Faculty of Medicine, Budapest, Korányi Sándor u. 2/a, Budapest, 1083, Hungary. takacs.istvan@med.semmelweis-univ.hu.
authors.forename: István
authors.initials: I
authors.lastname: Takács
mesh_terms: D000328:Adult; D000368:Aged; D002318:Cardiovascular Diseases / Q000097:blood* / Q000453:epidemiology; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D006814:Hungary / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D010281:Parathyroid Hormone / Q000097:blood*; D012621:Seasons; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood; D014808:Vitamin D Deficiency / Q000097:blood / Q000453:epidemiology / Q000517:prevention & control
chemical_list: D010281:Parathyroid Hormone; D014807:Vitamin D; C104450:25-hydroxyvitamin D
keywords: Deficiency; Free vitamin D; PTH; Vitamin D