Effect of Vitamin D on Ovulation Rate in Women With Polycystic Ovary Syndrome

Inclusion Criteria: * Premenopausal * Aged 18-40 years * Irregular long menstrual cycles (\>35 days) * PCOS according to the Rotterdam criteria * Agree for transvaginal ultrasound Exclusion Criteria: * Use of hormonal medication (including contraception) within 3 months prior to study inclusion, except the use of a progestogen to induce withdrawal bleeding every 3 months * History of any medical condition or medications that may predispose to vitamin D sensitivity, altered vitamin D metabolism and/ or hypercalcemia, including active tuberculosis or current therapy for tuberculosis, sarcoidosis, history of renal/ ureteral stones, parathyroid disease, renal or liver failure or current use of anti-convulsants * Use of insulin-sensitizing drugs, lipid lowering drugs or anti-hypertensive * Anticipated to use the above medications in the coming one year * Known type 2 diabetes mellitus * Refusal to join the study * Abnormal blood calcium level For those on supplements, we asked them to stop their own supplements.