Abstract: ob＜x＞jective To investigate the li＜x＞nk between insulin resistance, estrogen and endometrial carcinoma and also to clarify the possible insulin mechanism of action in endometrial carcinoma.Methods 30 patients with pathologically confirmed endometrial cancer from January 2014 to January 2018 in Xuzhou Central Hospital gynecological hospitalization served as the study group. We selected 30 cases of normal endometrium that are at the same period due to uterine fibroids, uterine prolapse underwent hysterectomy as a control group. LC-MS/MS was used to detect the levels of estradiol in serum and pathological specimens (normal endometrium, cancer tissue and paracancerous tissues). Serum insulin was detected by enzyme-li＜x＞nked immunosorbent assay and fasting blood glucose was detected by glucose oxidase method. HOMA-IR = fasting insulin ×fasting blood glucose / 22.5. Insulin resistance was determined by HOMA-IR≥2.69. The levels of serum insulin and insulin resistance incidence were compared. Type I endometrial cancer patients with type 2 diabetes who underwent surgery in our hospital from January 2009 to January 2018 were retrospectively analyzed. And they were grouped into metformin-treated group, metformin-combined group, and other treated groups. The correlation between metformin and EC pathological type, me＜x＞tastasis and tumor proliferation index Ki-67 was analyzed. Endometrial carcinoma cells, Ishikawa and HEC-1-A, were cultured in serum-free medium and treated with insulin (1.0×10-6 mol/L INS), and insulin combined with metformin (1.0×10-6 mol/L INS+5 mmol/L Met). After treatment for 24 h, BrdU labeling method was used to detect the proliferation rate of three groups of cells. Real-time RT-PCR was used to detect the ex＜x＞pression of c-fos and c-myc mRNA in the three groups.Results The results of LC-MS/MS showed that the level of E2 in serum and cancer tissues of EC patients was significantly higher than that of the control group (P<0.05). Serum insulin (INS) was detected by enzyme-li＜x＞nked immunosorbent assay (ELISA), and fasting blood glucose (FBG) was detected by glucose oxidase assay. The results showed that the serum insulin level and the rate of insulin resistance in patients with endometrial cancer were significantly higher than those in the control group (P<0.05). Retrospective analysis showed that the tumor proliferation rate (Ki-67%) of patients treated with metformin was significantly lower than that of other drug treatment groups. Pathological data showed that the proportion of poorly differentiated adenocarcinoma and distant me＜x＞tastasis rate in patients treated with metformin were lower than those in other treatment groups, and the difference was statistically significant (P<0.05). The results of BrdU labeling showed that insulin had a significant proliferative effect on the two cells after 24 hours, and the difference was statistically significant (P<0.05). When the two cells were treated with metformin (5 mmol/L) combined with insulin (1.0×10-6 mol/L INS) for 24 h, the proliferative effect of insulin on both cells was significantly inhibited. The difference was statistically significant when compared with the INS group (Ishikawa: P<0.05, P=0.000; HEC-1-A: P<0.05, P=0.000) and control group (Ishikawa: P<0.05, P= 0.004; HEC-1-A: P<0.05, P = 0.000). Real-time RT-PCR results showed that c-myc and c-fos ex＜x＞pression in the two cells of the insulin group was significantly higher than that of the control group (P<0.05). The ex＜x＞pression levels of c-myc and c-fos of insulin combined with metformin group were significantly lower than those in the INS group (P<0.05). The difference was statistically significant compared with the control group (P<0.05). Conclusion The serum and tissues of patients with endometrial cancer have higher estrogen levels. Insulin resistance and its secondary high insulin levels may promote the development of endometrial cancer by affecting estrogen levels.