Abstract: Objective: To explore the factors affecting in weight loss-related amenorrhea with estrogen replacement therapy and clarify the variation of gonadotropin in patients recovered ovulation. Methods: The data of 36 patients with weight loss-related amenorrhea were collected and analyzed. Conjugate equine estrogens were given, BMI and gonadotropin level monitor were repeated in every follow-up. LHRH challenge test was carried out while in temporary cessation of ERT every 6 months. BBT and serum progesteone were used to detect ovulation. The factors affecting the time of ovulation recovery were analyzed by statistic comparing. Results: Twenty cases in the study resumed ovulation with the average time 24.1±13.6months, while the period by estrogen replacement therapy in non-recovered groups was only 6.65±3.36months. Treatment period by estrogen replacement therapy in patients with resumed ovulation was negatively correlated with former BMI (correlation efficiency=-0.69,p<0.01) and basal BMI (correlation efficiency=-0.59, p=0.04). 1kg/m₂ higher former BMI means 3.1 months. Significant increase of LH (1.2±0.4 vs 5.6±1.6 mIU/ml, P=0.005) and area under curve of LH in LHRH test (17.1±6.3 vs.44.6±10.1mIU/ml, P=0.027) were observed in the 20 recovered patients. Moreover, 17 had a mean increase of BMI by 1.92 ±2.11kg/m₂, 2 had unchanged, only one of 20 cases had a slightly decrease by 0.4kg/m₂.Conclusion: Weight loss-related amenorrhea could restore ovulation by estrogen replacement therapy. The lower former or basal BMI meaned the longer period of estrogen replacement therap. LH self-level elevation and its highly response to gonadotropin resumes by ERT made ovulating possible. BMI acquired was essential but not necessary to the recovery of ovulation.