title: The role of vitamin D in metabolic disturbances in polycystic ovary syndrome: a systematic review.
abstract: BACKGROUND
  Metabolic disturbances, in particular, insulin resistance (IR) and dyslipidemia, are common in women suffering from polycystic ovary syndrome (PCOS). Evidence is accumulating that vitamin D status may contribute to the development of metabolic disturbances in PCOS.
  
  
  OBJECTIVE
  The aim of this study was to carry out a systematic review addressing the association between vitamin D status, vitamin D receptor polymorphisms, and/or polymorphisms related to vitamin D metabolism and metabolic disturbances in women with PCOS.
  
  
  METHODS
  A systematic search of electronic databases was carried out up to January 2013 for observational studies and clinical trials in women suffering from PCOS with outcome measures that were related to vitamin D status. We conducted univariate and multivariate regression analyses of the weighted means to gain insights into the association between vitamin D, BMI, and IR based on existing literature.
  
  
  RESULTS
  We found 29 eligible trials with inconsistency in their results. One well-designed randomized controlled trial has been carried out until now. Univariate regression analyses of the weighted means revealed vitamin D to be a significant and independent predictor of IR in both PCOS and control women. The significance disappeared after adjustment for BMI in PCOS women.
  
  
  CONCLUSIONS
  Current evidence suggests an inverse association between vitamin D status and metabolic disturbances in PCOS. Owing to the heterogeneity of the studies, it is hard to draw a definite conclusion. The causal relationship between vitamin D status and metabolic disturbances in PCOS remains to be determined in well-designed placebo-controlled randomized clinical trials.
authors.affiliation: Department of Internal Medicine, Medical Centre Alkmaar, PO Box 501, 1800 AM Alkmaar, The Netherlands.
authors.forename: Y H M
authors.initials: YH
authors.lastname: Krul-Poel
authors.forename: C
authors.initials: C
authors.lastname: Snackey
authors.forename: Y
authors.initials: Y
authors.lastname: Louwers
authors.forename: P
authors.initials: P
authors.lastname: Lips
authors.forename: C B
authors.initials: CB
authors.lastname: Lambalk
authors.forename: J S E
authors.initials: JS
authors.lastname: Laven
authors.forename: S
authors.initials: S
authors.lastname: Simsek
mesh_terms: D015992:Body Mass Index; D005260:Female; D006801:Humans; D007333:Insulin Resistance; D011085:Polycystic Ovary Syndrome / Q000097:blood* / Q000378:metabolism; D011110:Polymorphism, Genetic; D018167:Receptors, Calcitriol / Q000235:genetics*; D014807:Vitamin D / Q000097:blood / Q000627:therapeutic use*; D014808:Vitamin D Deficiency / Q000097:blood* / Q000188:drug therapy / Q000378:metabolism; D014815:Vitamins / Q000097:blood / Q000627:therapeutic use*
chemical_list: D018167:Receptors, Calcitriol; C579457:VDR protein, human; D014815:Vitamins; D014807:Vitamin D