This study investigates the incretin effect in women with polycystic ovary syndrome (PCOS) before and after removal of their insulin resistance by metformin.

The investigators' hypothesis is that insulin resistant women with PCOS have a reduced incretin effect and elevated glucagon responses as measured by a 75-g oral glucose tolerance test and isoglycemic i.v. glucose infusion. The investigators hypothesise that both can be improved when their insulin resistance is removed.

Inclusion Criteria PCOS-women:

• Diagnosed with PCOS according to the Rotterdam criteria
• more than 18 years old
• BMI less than 30 kg/m2
• Normal glucose tolerance and fasting plasma glucose (assessed by 75-g OGTT)
• Negative GAD65 and islet cell autoantibodies
• Insulin resistant according to HOMA-IR
• informed consent

Inclusion Criteria healthy women:

• more than 18 years old
• BMI less than 30 kg/m2
• Normal glucose tolerance and fasting plasma glucose (assessed by 75-g OGTT)
• Negative GAD65 and islet cell autoantibodies
• informed consent
• regular menstrual cycle (28-35 days)
• Plasma androgen levels within reference levels

Exclusion Criteria PCOS and healthy women:

• First or second degree relatives with diabetes
• pregnancy or breast feeding
• treatment with medication which influences the glucose metabolism (incl hormonal contraception)
• Congenital diseases which cause hyperandrogenism and irregular bleeding
• Known adrenal hyperplasia
• Known hyperprolaktinemia
• Alcohol consumption of more than 20 grams a day
• Hemoglobin less than 7.8 %