Myoinositol vs. Metformin in Women with Polycystic Ovary Syndrome: A Randomized Controlled Clinical Trial

Polycystic ovary syndrome (PCOS) is associated with insulin resistance. Few randomized controlled trials (RCT) compared myoinositol (MI) with metformin (MET) regarding insulin resistance in PCOS. This was an open-label six-month RCT in women with PCOS (n = 45) with interventions MI 4 g/day or MET 2 g/day. Primary outcome was the homeostasis model assessment of insulin resistance (HOMA-IR). Secondary outcomes were fasting glucose, weight, cycle length, lipids, testosterone, adverse effects, quality of life, and depression scores. Median age was 26 years. Body mass was index was 34.4 kg/m2. HOMA-IR was unchanged during MI (p = 0.31) and MET (p = 0.11) (MI vs. MET, p = 0.09). Median fasting glucose changed +0.2 mmol/L during MI (p < 0.001) and −0.1 mmol/L during MET (p = 0.04) (MI vs. MET p < 0.001). Median weight changed −2.3 kg during MI (p = 0.98) and −6.1 kg during MET (p < 0.001) (MI vs. MET, p = 0.02). Median cycle length decreased nine days during MI (p = 0.03) and 13 days during MET (p = 0.03) (MI vs. MET, p = 0.93). High-density lipoprotein (HDL) changed +0.1 mmol/L during MET (p = 0.04) (MI vs. MET, p = 0.07). All other blood parameters and scores of quality of life and depression remained unchanged during MI and MET (all p > 0.06) (MI vs. MET, all p > 0.27). Adverse effects appeared in four women during MI and 16 women during MET (MI vs. MET, p = 0.001). In conclusion, there was no effect on the metabolic outcomes during MI, but positive effects on fasting blood glucose, weight, and HDL during MET. The effect on cycle length was comparable during MI and MET. Adverse effects were less frequent during MI.