The incidence of endometriosis has been on the rise in recent years, and as the population ages, more patients with endometriosis are entering perimenopause and late menopause. The traditional view is that ectopic endometrium is estrogen-dependent and tends to stabilize in postmenopausal women. One study found that 96.9% of women with EMs were not bothered by pelvic pain after menopause. The postmenopausal application of hormone replacement therapy (HRT) raises estrogen levels in women, thus bringing concerns about the progression of ectopic endometrium. In 1992, Barbieri et al. proposed an “estrogen window”, i.e., a range of estrogen concentrations within which menopause-related symptoms can be relieved, bone loss can be inhibited, and endometrial growth is not stimulated. This theoretically suggests that there may be a safe window of estrogen supplementation for every patient with EMs. Patients with EMs who require HRT include those with perimenopausal symptoms caused by low estrogen and symptoms of bone loss due to pseudo-menopausal therapies such as GnRHa, spontaneously menopausal patients who have not undergone adnexal resection, and surgically menopausal individuals following bilateral adnexal resection. I. Reverse add-on therapy and hormone supplementation The application of GnRHa and other pseudo-menopausal therapies for the treatment of endometriosis can produce side effects such as hot flashes, vaginal dryness, loss of libido and osteoporosis (average bone loss of 4%-6% after 6 months of treatment) caused by low estrogen. According to the doctrine of the “estrogen window” required for EMs treatment, these symptoms can be alleviated by using “reverse addition therapy”, i.e. maintaining estrogen levels at 30-40 pg/mL. Many studies have shown that reverse addition of appropriate estrogen does not affect GnRHa pseudo-menopause therapy, and estrogen supplementation is now routinely used for reverse addition therapy in pseudo-menopausal patients. There is no uniform standard for the time of initiation of reverse addition therapy. Nowadays, it is mostly advocated to start supplementation with small doses of estrogen and progestin in the second to third month of medication, which can maintain bone mass at a level that is safe for human body. Post-surgical hormone supplementation therapy 1. Conservative surgery: Due to ovarian surgery, some patients with EMs may experience premature ovarian failure or early menopause, and these women need to receive HRT until the mean age of menopause. And there is no direct evidence whether these women receive HRT until after the mean age of menopause or after normal age menopause in women with EMs. It has been shown that ectopic endometrium does not respond typically to continuous stimulation with sex hormones compared to in situ endometrium, and that ectopic endometrium has lower concentrations of estrogen and progesterone than in situ endometrium; ectopic endometrium has lower concentrations of local action factors and growth factors than in situ endometrium. Since the progesterone in the combination therapy is sufficient to inhibit the active endometrium in situ and the surrounding environment is much less than that of the endometrium in situ, the same dose of progesterone should be sufficient to inhibit the value added and development of the ectopic endometrium. Thus, it seems that EPT should be safe for postmenopausal patients with EMs. 2. Radical surgery: After radical surgery, patients may develop perimenopausal symptoms and require hormonal supplementation, but often endometrial lesions remain after surgery, and if estrogen is applied in excess, the growth of the residual lesions may be stimulated and symptoms may recur. The risk of recurrence varies between drugs. In this group of patients, although the uterus has been removed, progestin is recommended for the first 2 years of treatment if HRT is needed because of the presence of ectopic endometrium. III. Commonly used drugs for hormone supplementation therapy Single progestin: norethindrone 0.625-1.2mg/d; methoxyprogesterone 5.0mg/d. Single estrogen: nil estrol (Vernon) 2mg, once every 2 weeks. Combined estrogens (Pemeryl premarin) 0.3-0.625 mg/d; estradiol valerate (Tegretol) 1 mg/d; tibolone (tibolone) 1.25 mg/d. Due to the presence of ectopic endometrium, the hormone supplementation therapy regimen for patients with endometriosis can be guided by the following principles: EMs is not an absolute contraindication to HRT; HRT for patients with EMs indications and other contraindications are similar to those for general postmenopausal women. For women who are surgically menopausal after total hysterectomy and double adnexal resection without large residual lesions, HRT is feasible if follow-up can be guaranteed; for women with preserved uterus and ovaries, the risk of treatment is evaluated according to the size of the lesion. Continuous combination therapy or tibolone is recommended for HRT, regardless of whether the patient has a uterus or not; ultra-low doses of estrogen are recommended; and progestin usage should be continuous combination therapy, with cycle therapy not recommended. HRT can be started immediately after double adnexal resection, with or without delaying the start of treatment. For patients with recurrence of symptoms or unwilling to undergo HRT, other alternative therapies are recommended to reduce menopausal symptoms and protect bone health.