For early breast cancer women who are premenopausal, after receiving chemotherapy (neoadjuvant chemotherapy or adjuvant chemotherapy), not using OFS as ovarian suppression, AMH, E2 and FSH levels will be measured by blood sampling before chemotherapy, at the end of chemotherapy and 1 month, 3 months, 6 months, 12 months, 18 months and 24 months after chemotherapy. The menstrual status of patients will be also followed up. At several timing, investigators will analyze AMH level, E2 level, FSH level, proportion of unmeasured AMH (AMH≤0.02ng/ml), proportion of E2 that conforms to menopausal status (E2≤30ng/L), proportion of FSH that conforms to menopausal status (FSH \> 30U/L), proportion of persistent amenia (no menstruation from the end of chemotherapy to the evaluation time) and incidence of adverse reactions
