 Methods: 150 PCOS women with 25-hydroxyvitamin D cholecalciferol, 25OHD levels 30 ngml will be treated with vitD 20,000 IUwk or placebo in a 2:1 randomized controlled trial over 24 weeks and investigated for metabolic and endocrine parameters as well as vitD related genetic variants. In addition, 150 non-PCOS women with 25OHD 30 ngml will be treated with vitD 20,000 IUwk or placebo in a 2:1 randomized controlled trial over 24 weeks and investigated for metabolic and endocrine parameters as well as vitD related genetic variants. The response to vitD supplementation in both groups will be analysed according to genotype profiles. 