Abstract:Objective To explore the ideal model replication time and pathological changes of endocrine and metabolism in PCOS-IR (polycystic ovary syndrome with insulin resistance) rats. Methods The control group rats were fed with normal diet, and administered by the 0.5% carboxymethylcellulose sodium salt sodium (CMC-Na) daily. The model group rats were given a high-fat diet with 60% fat content, and the letrozole solution was administered daily. According to the feeding time, each group was subdivided into four subgroups on the 21st, 24th, 27th and 30th day, six in each subgroup. The body mass, ovarian volume and ovarian histological changes, endocrine and metabolic indicators were observed in each group. After fasting, the rats were tested for fasting blood-glucose (FPG). The rat serum ELISA kit was used to determine the sex hormone level, triglyceride (TG) and fasting insulin (FINS) levels, calculate ovarian index, Follicle stimulating hormone (FSH) /Luteinizing hormone (LH) ratio and insulin resistance index (homeostasis model of assessment for insulin resistence index, HOMA-IR). Results The body weight of the rats in the model group was significantly higher than that in the control group (P?0.05). The body mass and Lee’s index of the 27th d and 30th d model groups were significantly higher than the 21st d. The ovarian volume of the model group was significantly increased (P?0.05), and ovarian volume of the 30th d was significantly higher than the 21st d (P?0.05), and the ovarian surface was more visible. The dense vesicle-like dilated follicles showed polycystic changes in the ovary. The serum FSH/LH ratio and T level were significantly increased in each model group (P?0.05). In addition, serum TG was significantly increased (P?< 0.05); Rats at the 27th d and 30th d model groups showed a significant increase in FINS and HOMA-IR (P?< 0.05). Conclusion The rat model of PCOS-IR pathological features and endocrine and metabolic disorders was successfully established by continuous feeding of letrozole combined with high-fat diet for 27 days.