Endometrial thickening may be the result of pregnancy, ovarian dysfunction, endometrial polyps, endometrial cancer, and medication factors. There may be hazards such as affecting menstruation, infertility, and cancer risk. 1. Causes of endometrial thickening (1) Pregnancy: After pregnancy, due to the increase of estrogen and progesterone levels, it may also lead to physiological endometrial thickening. (2) Ovarian dysfunction: it may lead to abnormal secretion of estrogen, which may cause abnormal thickening of the endometrium due to long-term stimulation of the endometrium by estrogen without progesterone antagonism. (3) Endometrial polyp: mostly a benign lesion with overgrowth of localized glands and mesenchyme in the endometrium, which may also lead to thickening of the endometrium. (4) Endometrial cancer: after suffering from endometrial cancer, due to the stimulation of cancerous tissues, it will also cause abnormal thickening of endometrium. (5) Drug factor: some women take estradiol and other drugs for a long time, which may also cause endometrial thickening. 2. Endometrial thickening harm (1) affect menstruation: menstruation is caused by the cyclical shedding of the uterine lining, and endometrial thickening may lead to irregular vaginal bleeding, scanty menstruation, or menstrual dribbling. (2) Infertility: Excessive thickening of the uterine lining may lead to infertility as the fertilized egg may not easily attach to the uterus, affecting pregnancy. (3) Cancer risk: If the endometrium is thickened for a long time, it may also increase the risk of cancer. When endometrial thickening occurs, you should visit your local gynecologist as soon as possible.