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I want to start off by saying painful periods are NOT normal. I repeat, painful periods are not normal. Many women believe that dealing with menstrual cramps during their cycle is par for the course of being a woman. This is a false belief that is so easily accepted because of the the large percentage of woman who suffer from severe menstrual cramps. I will delve deeper menstrual cramps in another blog. However, today I wanted to talk all about endometriosis.

What is Endometriosis?

Endometriosis is a condition in which endometrial-like tissue, normally found in the inner lining of the uterus (the Endometrium), grows in areas outside of the uterus. This tissue can be found on your ovaries, fallopian tubes, rectum, bladder, and even in c-section scars. The endometrial-like tissue responds to both estrogen and progesterone when they are secreted during menstruation. This tissue continues to function as it does in the uterus. It thickens, breaks down, and bleeds during menstruation leading to inflammation and scarring (1). There is a similar condition to endometriosis known as adenomyosis, in which endometrial tissue is found in the myometrium of the uterus (the smooth muscle of the uterus). Both endometriosis and adenomyosis are very similar in pathophysiology.

Who gets Endometriosis?

The number of women diagnosed with endometriosis is on the rise. Today, there are more than 176 million woman world wide who have been diagnosed. Many women are misdiagnosed and improperly treated for many years before the correct diagnosis is made. The average time from onset of symptoms to diagnosis of women with endometriosis ranges from five to ten years (1). Endometriosis is present in 10% of reproductive aged women, and the average age at diagnosis is between 25-29. Adolescents are also effected by this condition. More than half of women under 20 years old who experience pelvic pain or dyspareunia (painful intercourse) have endometriosis (4).

Typically, around age 50, estrogen levels rapidly decrease and women who are post-menopausal notice a resolution in their symptoms. However, because of the use of iatrogenic or endogenous hormones, for example, post menopausal women using hormone replacement therapy, the disease can still be active and cause problems. In rare cases, men who are on long-term estrogen therapy have developed endometriosis (3).

Theories on the cause of Endometriosis

There are many theories on the etiology of endometriosis, sadly, none of these theories have been proven or can fully explain all of the mechanisms associated with the development of the condition (3). So in essence, the cause is still unknown and is likely a combination of many of the factors described below.

1. Retrograde Menstruation

One theory on the cause of endometriosis is retrograde menstruation, or the back flow of endometriotic tissue through the fallopian tubes and into the pelvic cavity. This retrograde flow, along with potential hematogenous (blood vessels) or lymphatic circulation, may result in the seeding and growth of endometrial tissue in ectopic sites (lung, brain, eye, etc.) (4). However, research has found that at least 90% of women have retrograde flow, and because many do not develop endometriosis, this theory may be missing a piece of the puzzle, such as hormonal, inflammatory, and immunological dysfunction. This theory also fails to explain how men have developed the condition when treated with estrogen.

2. Immunological Origin

The immune system/endometriosis connection is complex. I will briefly discuss some of the known immune abnormalities found in women with endometriosis, however, I will go further in depth in another blog. One of the roles of our immune system is to remove debris from retrograde menstruation. However, in women with endometriosis it has been found that there is reduced surveillance and clearance of endometrial cells by the immune system, allowing for implantation into ectopic sites (5). Research has also identified an increase in inflammation, and the concentration of immune cells (IL-1, IL-6, IL-8, and TNF-α), within the peritoneal cavity promoting adhesions and angiogenesis (5). The combination of these mentioned factors favor the growth and survival of ectopic endometrial cells.

3. Metaplasia Theory

In the Metaplasia theory, it is thought that extrauterine cells abnormally transform into endometrial cells via immunological and/or hormonal factors (6). These cells are thought to have originated from the abdominal peritoneum. In the Mullerian Metaplasia theory, it has also been hypothesized that endometriosis is the result of residual embryonic cells from the Wolffian or Mullerian ducts that develop into endometriotic lesions that are responsive to estrogen (6). This theory could explain why pre-pubertal girls are diagnosed with endometriosis. Nonetheless, it fails to account for lesions found outside of the Mullerian duct (6).

Although endometriosis has been a condition that has been around for over 100 years, there is still no clear cause. In addition to the above mentioned theories, environmental factors and genetics are also thought to play a role in the development of the condition.

Known Risk Factors

Although, the origin of endometriosis is not quite understood there are some risk factors that have been identified. Below are a list of women with an increased risk (7):

  • Early age at menarche: Woman who have their first period before the age of 10

  • Women who have a short menstrual cycle (<27 days), and long menstrual flow (>7 days)

  • Women with a first degree relative have a 6x higher risk of developing endometriosis

  • Women with a higher body mass index (BMI), lack of exercise, and a high fat diet. (Fat in the body produces estrogen)

Conversely, there is a decreased incidence of the condition in (7):

  • Smokers (Smoking decreases estrogen levels)

  • Women who exercise consistently from an early age

  • Women who eat a low fat, and low red meat diet