Under normal circumstances, the thickness of the endometrium of a woman is usually between 3 and 12 mm. If it exceeds 12 mm, it can cause a series of symptoms such as increased bleeding and incomplete menstruation. Persistent thickening of the endometrium is also known as endometrial hyperplasia, and there are various causes of endometrial hyperplasia, such as endocrine disorders, ovulation disorders, obesity, medications, and other causes. Endometrial hyperplasia is simply caused by a problem with one of the changes in the endometrium, which leads to the appearance of the disease. If the body has an endocrine disorder and estrogen levels remain high, continuous stimulation of the endometrium can cause endometrial hyperplasia. Irregular ovulation will also cause the endometrium to be continuously affected by estrogen for a longer period of time, without progesterone to counteract it, and the lack of cyclic secretion period will cause the endometrium to be in a proliferative state for a long time. If the body is too obese, the body’s ability to convert fat is strong, and the level of estrogen in the blood is high, thus causing continuous estrogenic influence and endometrial hyperplasia. In addition, taking some medications can also affect endocrine secretion, thus causing endometrial hyperplasia to some extent. In conclusion, the main cause of endometrial hyperplasia is the imbalance of estrogen secretion in the body. Therefore, women should develop good lifestyle habits and try not to have endocrine disorders.