Endocrine therapy is an important method of breast cancer treatment and is suitable for breast cancer patients with ER and/or PR positive hormone receptors. The purpose is to reduce the tumor recurrence rate and improve the overall survival rate. Endocrine drugs: 1. Tamoxifen 20mg/d×5 years is mostly used in premenopausal patients. Pay attention to contraception during the treatment and perform gynecological examination every six months to one year to know the thickness of endometrium through ultrasound. After taking tamoxifen for 5 years, patients are still in premenopausal state, some patients may consider extending the use of tamoxifen to 10 years, and patients with high risk of recurrence may be feasible for ovarian debulking. 2, postmenopausal patients are recommended to use third-generation aromatase inhibitors (letrozole, etc.), aromatase inhibitors and LHRH analogs can lead to decreased bone mineral density or osteoporosis, therefore, bone mineral density testing is routinely recommended before the use of these drugs, and later during the use of the drug, bone mineral density is monitored once every 6 months. And T-score (T-Score) was performed, T-Score of <-2.5 is osteoporosis, start treatment with bisphosphonates; T-Score of -2.5 to -1.0 is reduced bone mass, give vitamin D and calcium tablets treatment and consider using bisphosphonates; T-Score of >-1.0 is normal bone mass, bisphosphonates are not recommended. Endocrine therapy may be less effective when applied concurrently with chemotherapy and is usually used after chemotherapy, but can be used concurrently with radiation therapy and trastuzumab therapy. As endocrine drugs interfere with the body’s hormone metabolism, they may cause menstrual disorders or reversible amenorrhea, and may also cause symptoms such as body fat, sweating, hot flashes, etc. Generally, it does not affect the treatment, and should be adhered to take the medication on time.