Song 2017.

Study characteristics
Methods	Randomised controlled trial Location of the trial: quote: "Beijing, China" Method of randomisation: quote: "Randomization was performed using a random number table." Method of allocation concealment: not stated Source of funding: quote: "This study was supported by Capital Characteristic Clinic Project of China; Beijing Capital Foundation for Medical Science Development and Research; Clinical Technique Innovation Project of Beijing Municipal Administration of Hospitals; Beijing Municipality Health Technology High‐level Talent; Foreign technical and administrative talent introduction project in 2017, State Administration of Foreign Experts A airs, the P. R. of China."
Participants	Inclusion criteria: being Chinese, diagnosis of PCOS, aged between 18 and 40 years, BMI ≥ 24 kg/ m2, fasting insulin (FINS) > 10 mIU/L and no history of taking medication or dietary modification currently or for the preceding 3 months. The diagnosis of PCOS was made according to the Rotterdam criteria with the presence of at least two of the following three features: oligo‐ or anovulation, clinical and/or biochemical hyperandrogenism and ultrasound finding of polycystic ovaries (presence of 12 or more follicles in each ovary measuring 2 mm to 9 mm in diameter, and/or increased ovarian volume > 10 mL) Exclusion criteria: exclusion of other aetiologies (congenital adrenal hyperplasia, Cushing’s syndrome, androgen‐secreting neoplasms, hyperprolactinaemia, and thyroid disease). Exclusion criteria were ischaemic heart disease, clinically evident vascular disease, type‐2 diabetes with ketoacidosis, renal or hepatic impairment, severe infection, and malignant tumour. Number of women randomised: 240/120 OCP + MET: 60 OCP: 60 Number of women analysed: 120 OCP + MET: 60 OCP: 60 Number of withdrawal and reasons: 0 Summary characteristics: PCOS, aged between 18 and 40 years, BMI ≥ 24 kg/ m2, fasting insulin (FINS) > 10 mIU/L Age (years): OCP + MET mean (+ SD): 28.63 (5.12) OCP mean (+ SD): 27.68 (4.99) BMI (kg/m2): OCP + MET mean (+ SD): 27.00 (3.47) OCP mean (+ SD): 28.64 (4.89)
Interventions	Treatment: OCP (Ethinyl Estradiol 35 mcg Cyproterone acetate 2 mg) from the 5th day of menstruation for a period of 21 days + MET (500 mg/day/1 week then 500 mg twice a day/1 week then 500 mg three times a day) Control: OCP (Ethinyl Estradiol 35 mcg Cyproterone acetate 2 mg) from the 5th day of menstruation for a period of 21 days Duration: 3 months Co‐intervention(s): low‐fat diet and moderate daily physical activity
Outcomes	Primary outcomes: Adverse events: severe (requiring stopping of medication) and minor Secondary outcomes: Body weight (kg) BMI (kg/m2) Serum total testosterone (nmol/L) Free androgen index (FAI) (%)
Subjective outcomes	None
Objective outcomes	(a) clinical parameters: 1. Adverse events: severe (requiring stopping of medication) and minor 2. Body weight (kg) and/or BMI (kg/m2) (b) hormonal parameters: 1. Serum total testosterone (nmol/L) 2. Free androgen index (FAI) (%)
Notes	Authors contacted about the number of patient randomised in each group and number of withdrawal Power calculation: unclear RCT with 4 arms: OCP versus OCP + MET versus OCP + orlistat versus OCP + MET + orlistat
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: “Randomization was performed using a random number table.”
Allocation concealment (selection bias)	Unclear risk	Method of allocation concealment not stated Insufficient information available to permit a judgement of “low risk” or “high risk”.
Blinding of participants and personnel (performance bias) All outcomes	High risk	Quote: “The trial was a randomized, open‐label, and parallel study”
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Insufficient information available to permit a judgement of ‘low risk’ or ‘high risk’. Blinding not stated.
Incomplete outcome data (attrition bias) All outcomes	Low risk	No missing outcome data.
Selective reporting (reporting bias)	Unclear risk	Body weight, BMI, BP pre‐specified in the methods not stated in the results But not a primary or key outcomes. Insufficient information available to permit a judgment of 'low risk' or 'high risk'.
Other bias	Low risk	The study appears to be free of other sources of bias.