Thickening of the endometrial lining is caused when there is an excess of the hormone estrogen without the corresponding female hormone, progesterone, states Healthline. When this occurs it is known as endometrial hyperplasia.
Throughout the month, the endometrial lining of the uterus constantly changes, according to the American Congress of Obstetricians and Gynecologists. During the first part of the month, the ovaries release estrogen, which causes the lining of the uterus to thicken and grow. Then, during the middle of the month, an egg is released from the ovaries into the uterus, which triggers the release of progesterone. Progesterone is the hormone that prepares the endometrial lining to nourish an egg if its fertilized. However, if the egg is not fertilized this means that pregnancy did not occur, and the levels of both progesterone and estrogen should decrease to start the monthly cycle and release the endometrial lining.
However, when an egg is not released from the ovaries, progesterone is not released either, according to the American Congress of Obstetricians and Gynecologists. When this happens, the endometrial lining is not shed and can continue to grow as estrogen is released, which leads to a thickening of the endometrial lining. The condition, endometrial hyperplasia, can lead to cancer but is not necessarily a cause of cancer. The cause of uterine cancer, according to Healthline, is a genetic mutation that causes normal endometrial cells to become abnormal cells that continue to replicate into other abnormal cells.
Risk factors for uterine line thickening include polycystic ovarian syndrome, a disorder that affects the levels of hormones in women; obesity; diabetes; and menopause, reports Healthgrades. Tracking menstrual periods, keeping diabetes under control and losing weight if overweight help to reduce the chances of endometrial hyperplasia. Taking birth control pills and, with the help of doctor, undertaking hormone replacement therapy may help as well.
Signs and symptoms include missed menstrual periods, acne, heavy bleeding during menstruation and bleeding between periods, notes Healthgrades. Other symptoms include hot flashes, tenderness of the vagina, dry vagina and mood swings. Rapid pulse, extreme abdominal pain, loss of consciousness and fainting require immediate medical attention.