The purpose of this study is to assess the efficacy and safety of dapagliflozin on improving insulin resistance and hyperandrogenemia in obesity women with polycystic ovary syndrome.

Inclusion Criteria:

1. women aged 18 to 45 years;
2. Subjects with PCOS diagnosed by according to the Rotterdam criteria;
3. BMI ≥24 kg/m2 and/ or Homeostatic model assessment of insulin resistance (HOMA-IR) with a cutoff ≥2.5;
4. No pregnancy plan within the next 6 months;

Exclusion Criteria:

1. Congenital adrenal hyperplasia such as 21-hydroxylase deficiency, hyperprolactinemia, Cushing syndrome, androgen-producing tumors of the adrenal gland or ovary;
2. Other endocrine diseases include poorly controlled thyroid diseases (hyperthyroidism or hypothyroidism), acromegaly, type 2 diabetes;
3. Patients with a history of acute / chronic infection, severe cardio-cerebrovascular diseases and acute / chronic pancreatitis;
4. Taking any antidiabetic medication that would affect insulin resistance or hyperandrogenemia (i.e. TZD, GLP-1RA, DPP-4i, metformin) in the past one month;
5. Taking letrozole, clomiphene, oral contraceptive, glucocorticoid, gonadotropin, gonadotropin releasing hormone agonist, anti-androgen drug (spironolactone, cycloproterenone acetate, Flutamide etc.) and/or other drugs for PCOS in the past three months;
6. History of recurrent urinary tract infection;
7. History of malignant tumor;
8. Currently participating in weight loss programs or weight change in the past 3 months (> 5% current body weight) or have a history of gastrointestinal surgery.
9. Serious liver dysfunction or chronic kidney disease (AST or ALT > 3 times the upper limit of normal, or eGFR<30 ml/min/1.73 m2);
10. Women who are pregnant or plan to become pregnant;
11. Subject is, in the judgment of the Investigator, unlikely to comply with the protocol or has any severe concurrent medical or psychological condition that may affect the interpretation of efficacy or safety data;
12. Participation in other clinical trial in the 4 weeks before randomization;
13. Patients who are unwilling or unable to give informed consent.