Background: Our aim was to assess the effects of metformin on menstrual frequency, fasting plasma glucose (FPG), insulin resistance assessed as HOMA-index, weight, waist/hip ratio, blood pressure (BP), serum lipids, and testosterone levels in women with polycystic ovary syndrome (PCOS) METHODS: In a randomized, controlled, double-blinded setup, 56 women aged 18-45 with PCOS were treated with either metformin 850 mg or placebo twice daily for 6 months. After a wash-out period of 3 months participants received the alternate treatment for 6 months. The changes in the measured parameters were analysed by intention-to-treat and per protocol.
Results: There were no changes in menstrual frequency. In the intention-to-treat analysis, weight and systolic BP were reduced on metformin treatment (p=0.009 and 0.047, respectively), while high-density lipoprotein (HDL) increased (p=0.001). On placebo, weight and FPG increased (p<0.05). Post-hoc subgrouping according to BMI revealed reductions in testosterone (p=0.013), FPG (p=0.018), insulin (p=0.045) and HOMA-index (p=0.022) in obese women. Per protocol analysis showed the following differences between the changes on placebo and metformin (mean (5 - 95 % percentiles): weight (-4.2 (-7.0, -1.9) kg, p<0.001), FPG (-0.23 (-0.44, -0.01) mmol/l, p=0.041), insulin (-4.17 (-8.10, -0.23) mIU/l, p=0.039) and HOMA index (-1.50 (-2.53, -0.47) mIU/l*mmol/l, p=0.006). Weight, FPG and HOMA index were lower after metformin than after placebo.
Conclusions: Metformin treatment lowered weight and systolic blood pressure and increased HDL in women with PCOS. In post-hoc analysis it increased insulin sensitivity and lowered testosterone in obese women. Non-obese women did not benefit from metformin.