When adenomyosis strikes, here's what's going on: A woman's uterus is lined with endometrial tissue (called the endometrium), and when a woman has adenomyosis, her endometrium is growing in the wrong place -- into the muscular layer of the uterine wall (called the myometrium). This abnormal growth may cause heavy menstrual bleeding (sometimes with blood clots called menorrhagia), pelvic pain, painful menstruation and severe menstrual cramps (called dysmenorrhea) and painful sex, as well as vaginal bleeding between menstrual cycles [source: Mayo Clinic]. Sometimes, the condition causes an abnormal mass called an adenomyoma to grow in the uterus. And yet, some women have mild symptoms such as tenderness or bloating in the pelvic region, and as many as 35 percent of those affected actually don't seem to have any apparent symptoms at all [source: Levgur].
And the cause behind the condition? Here's where things begin to get a little fuzzy.
Women who have gone through childbirth seem to be at a higher risk for developing adenomyosis, possibly due to inflammation in the lining of the uterus after giving birth. The risk also appears to increase for women who have given birth via cesarean section (c-section), terminated a pregnancy, undergone fibroid removal or had any other type of uterine surgery.
Current research is exploring a few possible causes behind the disorder, including uterine inflammation as mentioned above, invasive tissue growth and a theory known as developmental origins. The developmental origins theory suggests women with adenomyosis suffer from the condition because of how their uterus formed during fetal development. The invasive tissue growth theory suggests that when a woman undergoes uterine surgery, such as a c-section or a myomectomy to remove fibroids, cells from her uterine lining may unintentionally get pushed into the myometrium, triggering the condition.
Adenomyosis may also be hormone-triggered, an estrogen-dependent disorder caused by high levels of estrogen, progesterone, prolactin and follicle-stimulating hormone (FSH) circulating in the body. Women with the hormone-triggered version of the condition usually find it resolves itself once they hit menopause and their estrogen levels drop.
There are treatments for the condition, or at least ways to ease the symptoms.