Teng 2007.

Study characteristics
Methods	Randomised controlled trial Location of the trial: quote: "Harbin" Method of randomisation: quote: "Randomly assigned to two groups" Method of allocation concealment: not stated Source of funding: not stated
Participants	Inclusion criteria: Rotterdam criteria Exclusion criteria: ? Number of women randomised: 32 MET: 16 OCP: 16 Number of women analysed: 32 MET: 16 OCP: 16 Number of withdrawal and reasons: 0 Summary characteristics: PCOS
Interventions	Treatment: MET from Day 5, 500 mg/time, three times a day, ½ hour after meal Control: OCP (Ethinyl Estradiol 35 mcg/ Cyproterone acetate 2 mg) from Day 5, one pill per day, continues for 21 days Duration: 3 months Co‐intervention(s): none
Outcomes	Primary outcomes: none Secondary outcomes: BMI (kg/m2) Serum total testosterone (nmol/L) Fasting insulin (mIU/L) Fasting glucose (mmol/L)
Subjective outcomes	None
Objective outcomes	(a) Clinical parameters BMI (kg/m2) (b) Hormonal parameters Serum total testosterone (nmol/L) (c) Metabolic parameters Fasting insulin (mIU/L) Fasting glucose (mmol/L)
Notes	Power calculation: no
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "Randomly assigned to two groups" Insufficient information about the sequence generation process available to permit a judgement of 'low risk' or 'high risk'
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	Unclear risk	Insufficient information available to permit a judgement of ‘low risk’ or ‘high risk’. Blinding not stated.
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)	Low risk	The study protocol is not available but it is clear that the published reports include all expected outcomes, including those that were pre‐specified.
Other bias	Low risk	The study appears to be free of other sources of bias.