The causes of endometrial thinning include the following: first, congenital factors, some women are born with thin endometrium; second, the operation of the uterine cavity, women with a history of abortion, the existence of a history of uterine cavity operations, easily cause uterine adhesions or damage to the endometrium; third, endometrial tuberculosis, tuberculosis virus is easy to attack the reproductive organs, resulting in endometrial tuberculosis, erosion of the endometrium, resulting in its gradual thinning; fourth, the birth control ring Frequent operations, odor of the IUD and various surgical operations such as IUD removal repeatedly damage the endometrium, leading to its gradual thinning. These reasons are most of the reasons for the thinning of the endometrium.