Metformin has multiple health promoting effects and it may serve as a preventive measure for individuals who are at high risk for metabolic complications.

According to the latest international guidelines it should be considered as an adjunct therapy to lifestyle intervention in all overweight/obese women with PCOS, independently of their glucose homeostasis and menstrual regularity. However, there is no clear answer for how long metformin should be prescribed in this subset of women with PCOS and for how long the beneficial impact would sustain after treatment cessation.

The investigators compared the consequences of metformin withdrawal after long-term therapy as opposed to the consequences of metformin suspension after short term therapy in overweight/obese women with PCOS that had previously responded to metformin by means of moderate weight loss, improved menstrual frequency and sustained normal glucose homeostasis.

Inclusion Criteria:

• PCOS defined by the National Institute of Child Health and Human Development (NICHD) criteria
• obesity with body mass index ≥ 30 kg/m2
• normal glucose homeostasis at metformin treatment

Exclusion Criteria:

• known type 1 or type 2 diabetes mellitus
• heart failure
• renal insufficiency with serum creatinine more than 125 umol/L
• arterial hypertension
• pregnancy
• BMI below 25 kg/m2

The investigators conducted 20 obese women with PCOS with normal glucose homeostasis (without known type 1 or type 2 diabetes mellitus) who have been treated with metformin for one year prior to the study and 20 obese women with PCOS with normal glucose homeostasis (without known type 1 or type 2 diabetes mellitus) who have been treated with metformin for at least three years prior to the study.