When estrogen is produced, it stimulates the thickening of the endometrium or the lining of the uterus, according to Everyday Health. In premenopausal women, this occurs when estrogen levels rise during a stage of the menstrual cycle. The lining is then shed during menses. Postmenopausal women do not experience various endometrial thickness due to the lack of a monthly menstrual cycle; however, if a woman has an abnormally thick endometrium, further evaluation is needed to rule out endometrial cancer.
The excessive thickening of the endometrial lining is often due to an overproduction of estrogen without progesterone, explains the American Congress of Obstetricians and Gynecologists. When ovulation fails to occur, there is no production of progesterone and the endometrial lining does not shed. The endometrium then continues to thicken due to the production of estrogen, and the cells inside the lining can group together and lead to a condition known as endometrial hyperplasia.
Certain diseases can lead to hormonal changes that affect a patient's estrogen and progesterone production, reports Healthline. This can then result in endometrial thickening and an increased risk for cancer and cell abnormalities. The risk factors for endometrial cancer include diabetes, polycystic ovarian syndrome, endometrial polyps and obesity. Doctors diagnose endometrial cancer by conducting a transvaginal ultrasound and looking for abnormal endometrial thickness.