title: Seasonal variation in serum 25-hydroxy vitamin D3 does not affect 1,25-dihydroxy vitamin D.
abstract: The seasonal variation of serum 25-hydroxy vitamin D3 and 1,25-dihydroxy-vitamin D has been investigated. Blood was taken from 27 healthy volunteers, aged 21-44 years old at 3 monthly intervals over a period of 1 year. A scrolling monthly programme with 12 quarterly (3 month) time periods was developed. A summer associated increase in 25-hydroxy vitamin D3 was significantly correlated with but lagged behind by 2 months, the increase in recorded sunlight hours. However, four individuals showed no seasonal rise but maintained constant concentrations throughout the year within the established reference range. Serum 1,25-dihydroxy vitamin D showed marked intra-individual variability with no seasonal pattern although the highest concentration (180 pmol/L) was observed in the winter and no concentration greater than 108 pmol/L in the summer.
authors.affiliation: Department of Clinical Chemistry, Royal Liverpool University Hospital, UK.
authors.forename: T J
authors.initials: TJ
authors.lastname: Hine
authors.forename: N B
authors.initials: NB
authors.lastname: Roberts
mesh_terms: D000328:Adult; D002112:Calcifediol / Q000097:blood*; D002117:Calcitriol / Q000097:blood*; D005260:Female; D006801:Humans; D008027:Light; D008297:Male; D012016:Reference Values; D012621:Seasons
chemical_list: D002117:Calcitriol; D002112:Calcifediol