title: Seasonal variation of serum vitamin D among Greek female patients with osteoporosis.
abstract: OBJECTIVE
  Vitamin D (vitD) levels are positively associated with bone health and seasonality affects serum vit D. The aim of the study was to investigate the degree of seasonal variation on 25-hydroxyvitamin D (25(OH)D) serum levels in a population-based cohort of post-menopausal women with osteoporosis.
  
  
  METHODS
  Serum levels of 25(OH)D were assessed in 596 patients (mean age=65.3 years; standard deviation (SD)=9.4) in different time points over a period of 2.5 years.
  
  
  RESULTS
  The minimum 25(OH)D serum levels were observed in March (13.4±9.5 ng/ml) and the maximum levels in August, September and October (29.1±16.1, 28.9±12 and 28.4±8.9 ng/ml, respectively). The prevalence of vitD deficiency, insufficiency and sufficiency in March was 76.5, 15.7 and 7.8%, respectively. On the contrary, the highest prevalence of vitD sufficiency was observed in August, September and October (38.1%, 45.3% and 46.5%, respectively).
  
  
  CONCLUSIONS
  Seasonal variations should be considered when measuring for 25(OH)D serum levels and treating vitD deficiency.
authors.affiliation: Department of Endocrinology, Anticancer Hospital of Piraeus "Metaxa", Piraeus, Greece george.papadakis.md@gmail.com.
authors.forename: Georgios
authors.initials: G
authors.lastname: Papadakis
authors.affiliation: Department of Endocrinology, Anticancer Hospital of Piraeus "Metaxa", Piraeus, Greece.
authors.forename: Ioannis
authors.initials: I
authors.lastname: Keramidas
authors.affiliation: Department of Otolaryngology, Anticancer Hospital of Piraeus "Metaxa", Piraeus, Greece.
authors.forename: Kassiani
authors.initials: K
authors.lastname: Kakava
authors.affiliation: Department of Endocrinology, Anticancer Hospital of Piraeus "Metaxa", Piraeus, Greece.
authors.forename: Theodora
authors.initials: T
authors.lastname: Pappa
authors.affiliation: Biochemical Department, Anticancer Hospital of Piraeus "Metaxa", Piraeus, Greece.
authors.forename: Vassiliki
authors.initials: V
authors.lastname: Villiotou
authors.affiliation: Department of Endocrinology, Anticancer Hospital of Piraeus "Metaxa", Piraeus, Greece.
authors.forename: Eleni
authors.initials: E
authors.lastname: Triantafillou
authors.affiliation: Department of Endocrinology, Anticancer Hospital of Piraeus "Metaxa", Piraeus, Greece.
authors.forename: Aspasia
authors.initials: A
authors.lastname: Drosou
authors.affiliation: Department of Endocrinology, Anticancer Hospital of Piraeus "Metaxa", Piraeus, Greece.
authors.forename: Athanasia
authors.initials: A
authors.lastname: Tertipi
authors.affiliation: Department of Endocrinology, Anticancer Hospital of Piraeus "Metaxa", Piraeus, Greece.
authors.forename: Victoria
authors.initials: V
authors.lastname: Kaltzidou
authors.affiliation: Department of Endocrinology, Anticancer Hospital of Piraeus "Metaxa", Piraeus, Greece.
authors.forename: Anastasios
authors.initials: A
authors.lastname: Pappas
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D008875:Middle Aged; D010024:Osteoporosis / Q000097:blood* / Q000453:epidemiology; D015995:Prevalence; D012621:Seasons; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood
chemical_list: D014807:Vitamin D; C104450:25-hydroxyvitamin D
keywords: osteoporosis; seasonal variation; vitamin D