Hyperplasia of the endometrium is caused by long-term estrogen stimulation and lack of progesterone antagonism, and is clinically common in women around 50 years of age, and less common in those younger than 30 years of age. In addition, postmenopausal treatment with estrogen without progestin, polycystic ovary syndrome, obesity, and diabetes are all high-risk factors for endometrial hyperplasia. It can be divided into endogenous and exogenous estrogen increase: I. Endogenous estrogen increase: 1. Non-ovulation: When puberty, perimenopause, hypothalamic-pituitary-ovarian axis dysregulation, and polycystic ovary syndrome, non-ovulation is seen. This is due to the continuous stimulation of the endometrium by estrogen without progesterone counteracting it, and the endometrium is in a proliferative state for a long time, lacking the transformation of the cyclic secretion period. 2. Obesity: androstenedione secreted by the female adrenal gland can be catalyzed by aromatase in adipose tissue to produce estrone. As a result, obese women have higher plasma levels of estrone, resulting in persistent estrogen; 3. Endocrine functional tumors: abnormal gonadotropic function of the pituitary gland and ovarian granulosa cell tumors can lead to persistent estrogen secretion; 4. Other: including premature menarche, late menopause, and infertility can lead to abnormal sex hormone secretion, mainly due to high estrogen levels, and a history of hypertension, diabetes, and breast cancer are are high-risk factors. Exogenous estrogen increase: 1. Estrogen replacement therapy: Perimenopausal or postmenopausal women apply estrogen replacement therapy due to the lack of estrogen in their bodies. However, estrogen replacement therapy using estrogen alone without using progestin at the same time can stimulate excessive endometrial hyperplasia; 2. Long-term application of tamoxifen: Tamoxifen has anti-estrogenic effect, so it is used for postmenopausal patients with advanced breast cancer. However, when women have low estrogen levels, tamoxifen has weak estrogen-like effects, so long-term use can cause excessive endometrial hyperplasia.