Endometriosis is defined by the presence of endometrial glands and stroma outside the uterus. Here are some quick facts about the disease:
- Endometriosis affects 6 to 10% of reproductive age women.
- Up to 35 to 50% of women with infertility and/or pelvic pain have endometriosis.
- The average time between the onset of symptoms and a diagnosis of endometriosis is over six years.
- There is also a strong genetic link with endometriosis. If one of your first-degree relatives has endometriosis, then you are six times more likely to have endometriosis, too.
There are several theories on the origins of endometriosis, but the most common cause is retrograde menstruation with subsequent implantation of the tissue throughout the pelvis. What happens with retrograde menstruation is endometrial tissue is shed not only vaginally but up through the fallopian tubes and into the pelvic cavity. This was first described in the 1920s.
So if 90% of women have retrograde menstruation— why don’t all women have endometriosis?
I’ll describe the science behind what happens to women that will develop endometriosis:
- The ectopic endometrial cells are genetically altered which allows them to implant and survive outside the uterine cavity.
- These cells respond to hormone changes that occur throughout the menstrual cycle.
- The immune system, which is also altered, can no longer do its job of getting rid of these abnormal cells.
- Factors that cause inflammation are released. This promotes the growth of small vessels and nerves that allow the necessary blood supply for continued survival and contribute to the pain associated with endometriosis.
Additional inflammatory substances are also released that contribute to symptoms of the disease and can cause pain. These lesions may progress, forming scar tissue throughout the pelvic cavity, leading to further pain and/or infertility.
Some women with endometriosis form endometriomas, also known as “chocolate cysts.” Controversy exists on how women develop endometriomas but here are three current theories in the field:
- Endometriomas form from accumulated endometrial debris that gets “swallowed up” by the ovary.
- Endometriomas form from a preexisting ovarian cyst.
- Cells on the surface of the ovary change into endometrial tissue. This endometrial tissue multiplies and bleeds, ultimately forming an endometrioma.
If you are concerned that endometriosis may be contributing to your inability to get pregnant or have noticed worsening pain with your periods, I would encourage you to talk with your OB/GYN or see a reproductive endocrinologist (fertility specialist).
In my next post, I will discuss surgery treatment options for endometriosis.
Sampson JA. Metastatic or embolic endometriosis, due to the menstrual dissemination of endometrial tissue into the venous circulation. Am J Pathol. 1927;3:93–110.
Nnoaham KE, Hummelshoj L, Webster P, d’Hooghe T, de Cicco Nardone F, de Cicco Nardone C, et al. Impact of endometriosis on quality of life and work productivity: a multicenter study across ten countries. Fertil Steril. 2011;96:366–73.e8
Dr. Colleen Casey is a reproductive endocrinologist at the Center for Reproductive Medicine in Minnesota. She received her medical degree from the University of Minnesota, is a Fellow of the American College of Obstetrics and Gynecology and is board certified in Reproductive Endocrinology and OB/GYN. She completed her OB/GYN residency at the University of Michigan, where she received the resident of the year teaching award from medical students. She completed her reproductive endocrinology fellowship at the University of Vermont in 2008. Dr. Casey’s main research has focused on how hormones relating to obesity alter reproductive potential. Dr. Casey specializes in the evaluation and treatment of complex infertility problems. This includes all aspects of female and male infertility, Polycystic Ovarian Syndrome (PCOS), endometriosis, diminished ovarian reserve and recurrent pregnancy loss.