Whether or not it is dangerous for a 47-year-old woman to have an endometrial thickness of 20mm cannot be generalized. Endometrial hyperplasia without atypical hyperplasia is usually not dangerous; endometrial atypical hyperplasia is relatively dangerous; and adenocarcinoma of the endometrium is more dangerous. 1. Endometrial hyperplasia without atypical hyperplasia: the endometrium is simple hyperplasia, which belongs to endometrial hyperplasia. It can be treated with medication, and usually can be treated with progesterone to transform the endometrium, which is usually not dangerous. 2. Atypical endometrial hyperplasia: relatively dangerous, belongs to precancerous lesions, and should be actively intervened. The treatment depends on the actual situation of the patient, and surgery is usually chosen. 3. Endometrial adenocarcinoma: endometrial cancer is relatively dangerous and requires active treatment. Treatment is mainly based on surgery, generally the uterus and bilateral adnexa should be removed, and the scope of surgery should be decided according to clinical staging. If the endometrium is 20mm thick, you should consult the doctor in time, conduct relevant examination under the doctor’s guidance, make a clear diagnosis and standardize the treatment.