Patients often come with post-operative pathology reports and ask what ER and PR are and what they have to do with breast cancer. In fact, this is what we usually call hormone receptor testing and endocrine therapy for breast cancer. Endocrine therapy for breast cancer originated from Beatson’s first report in 1896, in which two cases of advanced premenopausal breast cancer were treated with bilateral oophorectomy and the development of tumor was controlled in remission, and one of them regressed 8 months after surgery. Since then, people have started the continuous exploration of endocrine treatment for breast cancer. The breast is an organ closely related to endocrine hormones, and estrogen is directly related to the development of breast cancer; studies have shown that estrogen and progesterone bind to and activate estrogen receptors (ER) and progesterone receptors (PR) on breast epithelial cells, which can lead to proliferation of normal breast epithelial cells, and proliferating cells are more sensitive to carcinogenic substances than resting cells, suggesting that they are tumor promoters and can More than 50% of breast cancers are hormone-dependent tumors, which is the mechanism of endocrine therapy for breast cancer and the difference between breast cancer treatment and other cancers. The advantages of endocrine therapy are: 1) it has less impact on normal cells and has much less side effects compared to chemotherapy, and the efficacy is no worse than chemotherapy as long as the case is properly selected; 2) it takes 2-8 weeks to take effect, but once it is effective, the maintenance time is longer; 3) the treatment cost is lower, and because the toxic side effects are lighter and less, there is no need for whitening and antiemetic treatment. Therefore, it has a very important position both as an adjuvant treatment to prevent recurrence and metastasis after breast cancer surgery, and as a relief treatment after recurrence and metastasis. Postoperative adjuvant endocrine therapy for breast cancer can reduce the risk of recurrence and metastasis and death. Patients with positive estrogen or progesterone receptors should receive adjuvant endocrine therapy regardless of their age, menstrual status, tumor size, and whether their lymph nodes are metastatic or not. The following drugs are now commonly used: tamoxifen (triamcinolone), which is indicated for all stages of pre- and post-menopausal breast cancer, and aromatase inhibitors (letrozole, alatriptan, exemestane), which are mainly used for post-menopausal breast cancer and are more effective than triamcinolone in post-menopausal patients. The current recommended optimal duration of administration is 5 years in a row. Patients who are on triamcinolone acetonide and are judged by their doctors to be menopausal can also be switched to an aromatase inhibitor. Surgical or pharmacologic ovarian debulking (goserelin, leuprolide) is also an option for premenopausal women at high risk. Endocrine therapy for advanced breast cancer can be used alone or in sequence with chemotherapy depending on the recurrence of metastasis, mainly to relieve symptoms and prolong survival. The efficiency of endocrine therapy for double receptor positive breast cancer patients is 60-70%, while the efficiency for receptor negative patients is less than 10%. Again, appropriate drugs need to be selected according to the menstrual condition, and available drugs are progestins in addition to the above mentioned drugs. There is less cross-resistance between endocrine drugs, and after the failure of one drug, another drug can be tried. The role of endocrine therapy in breast cancer treatment has been universally recognized and fully confirmed by research, and it is a powerful weapon for breast cancer patients to fight against the tumor. There are still many studies on endocrine therapy being conducted internationally, and the results of these studies will further guide patients’ treatment and provide strong evidence for more individualized treatment.