Effect of probiotic and metformin combination therapy on insulin resistance in polycystic ovary syndrome compared with metformin alone

Background: Insulin resistance in PCOS can be aggravated by gut microbiota dysbiosis. Probiotics may improve microbial balance and insulin sensitivity and, in combination with metformin, improve glycemic control while reducing side effects. This study aimed to compare the effects of probiotic–metformin combination therapy versus metformin alone on insulin resistance in PCOS patients. Methods: This randomized controlled trial at BSMMU included 60 infertile women with PCOS and insulin resistance. Participants were randomized into two groups: one received probiotics (Lactobacillus and Bifidobacterium, 4 billion CFU twice daily for 12 weeks) plus metformin and the control group received metformin alone. Fasting blood sugar and insulin were measured pre- and post-treatment to assess insulin resistance. Results: In the experimental group (probiotics+metformin), FBS, fasting insulin and HOMA-IR decreased significantly after 12 weeks (5.1±0.6 vs 5.5±0.9 mmol/l; 10.2±3.8 vs 17.5±5.5 µIU/ml; 2.3±0.9 vs 4.3±1.5). Similar significant reductions were observed in the control group (metformin alone) for FBS (5.3±0.6 vs 5.4±0.5 mmol/l), fasting insulin (10.8±4.3 vs 17.6±7.4 µIU/ml) and HOMA-IR (2.6±1.4 vs 4.2±1.6). However, the mean changes between groups were not statistically significant. Conclusions: Probiotic–metformin therapy improved insulin resistance, but not significantly more than metformin alone and had fewer, non-significant side effects.