If a woman is not yet menopausal, taking estradiol alone may promote thickening of the uterus or even lesions, which can produce endometrial cancer in severe cases. Estrogen may act on the glands of the breast, leading to breast enlargement or even abnormal masses and breast cancer. It may increase the risk of hypertension and blood clots. Patients who usually smoke or have elevated blood pressure and those with a family history of stroke are advised to use the drug with caution, as the drug is metabolized in the liver or kidneys, which may increase the burden on these two organs causing liver and kidney function damage. If combined with cervical cancer, endometrial cancer, breast cancer and other abnormal diseases, this drug cannot be taken which will lead to the deterioration of malignant diseases, so it is best not to use estrogen alone, but generally add progestin in the second half of the cycle.