The normal metabolism of the breast is resistant to the coordinated action of many hormones, especially estrogen and progesterone. These hormone receptors must bind to specific proteins in the cell in order to function, and these specific proteins are called estrogen receptors (ER) and progesterone receptors (PR). When cells become cancerous, the cells can partially or fully retain the normal estrogen and progesterone receptor systems, and the function of hormone receptors in tumor cells is similar to that of normal cells, indicating that the growth of the tumor cells still depends on the regulation of the original hormonal environment, which is called hormone-dependent tumors, accounting for about 55%-65% of breast cancers; on the contrary, some tumors completely lose their receptor systems during the cancerous process and can no longer function as hormone receptors. On the contrary, some tumors lose their receptor system and can no longer be used as hormone target cells, and their growth is no longer controlled and regulated by hormones. Accordingly, breast cancer is clinically classified into hormone receptor positive and hormone receptor negative tumors, and hormone receptor positive tumors receive endocrine therapy while hormone receptor negative tumors can only be treated with chemotherapy. Endocrine therapy for breast cancer has been used for more than 100 years, much earlier than the application of chemotherapy drugs. As early as 1890, Beatson first reported that removal of the ovaries could cause breast cancer to regress. Endocrine therapy for breast cancer is mainly used for hormone receptor-positive, hormone-sensitive tumors. Endocrine therapy has the advantages of easy administration, few adverse effects and long-lasting efficacy. There are the following common misconceptions in clinical application: 1. If breast cancer patients are hormone receptor positive, endocrine therapy is effective. Endocrine therapy for breast cancer is based on the combination of clinical information of patients and the expression status of estrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor (HER-2) in their tumor tissues to formulate the corresponding treatment plan and predict the treatment effect and assess the prognosis, therefore, the ER, PR and HER-2 test results of breast cancer patients are the basis for deciding how to choose the treatment plan. Therefore, ER, PR and HER-2 test results of breast cancer patients are the basis for choosing the treatment plan, and the test results are influenced by many factors, including the pre-treatment of specimens, fixation, test methods and laboratory quality control, interpretation of test results and standardization of pathology reports. The prerequisite of endocrine therapy for breast cancer patients is that the ER or PR must be positive, but ER and PR positive results are a large category, ER and PR positive means that 1 positive to 90 positive receptor expressions are called positive, and their efficacy can vary greatly. Currently, there is no standard to quantify the hormone expression status, some hospitals use weak positive, positive or strong positive to express it, but most hospitals only use positive to express it, because the effect of endocrine treatment for breast cancer is also related to age, whether or not chemotherapy is given, and whether or not there is obesity. Like all information in medical oncology, the treatment effect will not be 100%, even for patients with strong positive ER and PR, the effective rate is only about 75%, and the duration of treatment effect also varies individually. Therefore, even breast cancer patients with positive hormone receptors should undergo regular medical checkups at hospitals during endocrine therapy. 2. In breast cancer patients, hormone receptor positive expression will never change and endocrine therapy will always be effective. Currently, the only choice of endocrine therapy for breast cancer is based on the positive expression of ER and PR receptors in breast cancer tissue, which is usually selected based on the parameters at the time of primary tumor diagnosis, even for patients with metastatic cancer occurring several years later. Several studies at home and abroad have already found that the lack of concordance of tumor biomarkers between the primary tumor and metastatic sites diagnosed at the same time, and the biological behavior of the tumor after therapeutic intervention, can also appear or be lost, as shown by the original hormone receptor positivity, which is effective for endocrine therapy, and after chemotherapy or endocrine therapy, the hormone receptor expression is negative and endocrine therapy loses its effect; or the original hormone receptor negativity. After chemotherapy, the hormone receptor expression is positive and can receive endocrine therapy. In 2010, I reported a research project, “Temporal variability of biomarker expression status in breast cancer”, in which 168 breast cancer patients with long-term follow-up (>5 years) were tested at different time points, and ER, PR and human epidermal growth factor receptor (HER-2) were detected by immunohistochemistry. assays to compare the differences in the above biomarkers at different time points and also to analyze the relationship with the patients’ original treatment and post-recurrence treatment. Among the expression of hormone receptors, five cases showed down-regulation of ER expression, two cases showed up-regulation of ER expression, and two cases showed down-regulation of PR expression. This finding suggests that the expression of hormone receptors and HER-2 in breast cancer patients changes with time and treatment, and patients who develop recurrence or metastasis need to obtain tissue specimens again to test the above biomarkers. If it is difficult to obtain tissue specimens, it is necessary to closely observe the changes of the disease during treatment and change the treatment plan once the treatment effect is not satisfactory. 3.No adverse effects of endocrine therapy for breast cancer. With the introduction and improvement of endocrine therapy drugs year by year, the strategy of endocrine therapy for breast cancer is undergoing profound changes. With the successful development of the third generation aromatase inhibitors, its therapeutic status for breast cancer is becoming more and more obvious and gradually becomes an important means of endocrine therapy for breast cancer. However, all drugs are double-edged swords and can have adverse effects while treating tumors, and endocrine therapy for breast cancer is no exception. Tamoxifen, the first estrogen receptor antagonist introduced into clinical treatment in 1971, is regarded as a milestone in endocrine treatment of breast cancer. The mechanism of action of tamoxifen is complex, exhibiting an anti-estrogenic effect on the breast and a partial estrogen-like effect on the bone. In postmenopausal patients, because of its mild estrogen-like effects, it may prevent the progression of osteoporosis, while in premenopausal patients it may accelerate the loss of bone components. In addition, serious side effects of tamoxifen include endometrial cancer, thromboembolism, and the occurrence of cerebrovascular events, among others. During treatment with tamoxifen, pelvic ultrasound should be done regularly at the hospital and the thickness of the endometrium should be scraped or the medication should be changed to a certain value. Third-generation aromatase inhibitors, a class of drugs including letrozole, anastrozole and exemestane, are mainly indicated for postmenopausal breast cancer patients. Third-generation aromatase inhibitors can effectively inhibit 95-98% of aromatase activity, blocking the conversion of androstenedione and testosterone to estrogen via aromatization in tissues other than the ovaries, resulting in a significant reduction in estradiol levels, which inevitably has a complex effect on bone physiological processes in postmenopausal breast cancer patients, that is, leading to a decrease in the activity of osteoblasts and a relative increase in the function of osteoclasts, resulting in a decrease in bone mass There are several studies on the decrease in bone health due to third-generation aromatase inhibitors, and the conclusions are consistent. Therefore, it is recommended that for patients treated with third-generation aromatase inhibitors for osteoporosis prevention and treatment, the general preventive treatment is: oral calcium 1500 mg/d and vitamin D 400-800 IU/d; it is recommended to increase exercise, such as walking at least 4 times a week for at least 40 minutes each time.