Endometrial thinning is most commonly caused by the following two major clinical causes: first, endocrine disorders such as polycystic ovary syndrome, hyperprolactinemia, hyperthyroidism, hypothyroidism, hypovarianism, premature ovarian failure, etc. Patients need to have their sex hormones and thyroid function checked to identify the cause and choose the right medication. Patients need to have their sex hormones and thyroid function checked to identify the cause and choose the right medication for treatment. For polycystic ovary syndrome, DY-35 is the treatment of choice; for hyperprolactinemia, bromocriptine is the treatment of choice; for hyperthyroidism, methimazole is the treatment of choice; for hypothyroidism, thyroxine is the treatment of choice; for hypovarianism or premature ovarian failure, estrogen and progestin are the treatment of choice. The second is caused by organic lesions, such as endometrial damage and endometrial adhesions. In this case, hysteroscopy is needed to make a clear diagnosis and, if necessary, hysteroscopic electrodesis is needed, as well as estrogen and progestin for endometrial repair.