Polycystic Ovary Syndrome (PCOS) is one of the most common female endocrine disorders affecting approximately 5%-10% of women of reproductive age (12–45 years old) and is thought to be one of the leading causes of female infertility. Insulin resistance has been associated with abnormal endometrial development and endometrial defects in women with PCOS. In addition, women with PCOS are considered to be at increased risk of miscarriage after either spontaneous or assisted conception. Metformin, an insulin-sensitizing agent, has been reported to ameliorate the endothelial function of normal-weight PCOS subject through the improvement of insulin peripheral action.