Inclusion Criteria:

• Premenopausal women (ages 18-40 years) with normal thyroid function and prolactin levels.

• PCOS diagnosis based on Rotterdam criteria: presence of at least 2 of the following criteria:

  • oligomenorrhea-menstrual cycles > 35 day intervals
  • hyperandrogenemia (elevated serum testosterone [free or total] &/or androstenedione levels) or features of hyperandrogenism i.e. acne or hirsuitism [Ferriman-Gallaway score > 3]
  • polycystic ovaries on vaginal ultrasound as defined by ESHRE/ASRM criteria (ovarian volume ≥ 10mL or ≥ 12 follicles of diameter between 2-9mm in at least one ovary)
  • Overweight (BMI ≥ 27 Kg/m2)
  • Biochemical evidence of Vitamin D insufficiency (i.e. serum 25 OHD levels < 20ng/mL)

Exclusion Criteria:

• Pregnancy
• Known causes of oligomenorrhea other than PCOS, e.g. hypothyroidism/Cushing's Disease/late onset congenital adrenal hyperplasia (fasting 17-alphahydroxylprogesterone levels < 200ng/dL)
• Use of hormonal treatment (birth control pill/patch/depot medroxyprogesterone/medroxyprogesterone) within 3 months of the study onset.
• Use insulin sensitizers (metformin, sulfonylureas, TZDs, incretins) within 3 months of the study onset.
• Use of lipid lowering agents or medications known to influence insulin sensitivity (e.g. niacin, corticosteroids, beta blockers, calcium channel blockers, thiazide diuretics) or influence serum androgens (estrogen, anti-androgens, androgens) within 3 months of the study onset.
• Known history of renal calculi or current use of Calcium and Vitamin D supplements.
• Spanish Speaking.