Adenomyosis is a condition that occurs when the cells that normally line the uterus grow into the muscular tissue of the uterine wall. Most women who have adenomyosis have no symptoms. But it can cause heavy or prolonged menstrual periods (menorrhagia), painful menstruation (dysmenorrhea), and menstrual cramping that gradually gets worse from one period to the next.

The cause of adenomyosis is not fully understood. Some experts believe that it is the result of damage to the inner wall of the uterus during pregnancy, childbirth, or a surgical procedure. Symptoms can get worse with use of birth control pills. And symptoms can improve after menopause.

Adenomyosis pain and bleeding can be treated with nonsteroidal anti-inflammatory drugs (NSAIDs), a levonorgestrel intrauterine device (IUD), or in severe cases, removal of the uterus (hysterectomy).