INS and polycystic ovary syndrome: Due to the limited sample size (power calculation: the power values for BMI, waist circumference, testosterone level and fasting insulin level were 99.0, 96.9, 89.5, and 70.4% respectively, α = 0.0083) and the observation of association but not causality, further studies are needed to enlarge sample size and explore the potential causal mechanisms between gut microbiota and PCOS, such as the metabolites produced by gut microbiota and fecal microbiota transplantation.