What is endometriosis?

"I’m not here to give you a medical lecture. What matters to me is making endometriosis understandable, in a way that is accessible, clear, and human. Because knowledge is power.


For individuals living with endometriosis, understanding the condition is a crucial step toward empowerment, toward navigating care, making informed decisions, and living better with the disease.


For organizations, healthcare professionals, and policymakers, understanding endometriosis clearly is essential to designing better patient pathways, stronger awareness campaigns, and more effective policies.


Empowerment begins with clarity.
And clarity begins with understanding"


- Laura Lequeu

Endometriosis is a gynecological and multi-systemic (because it can affect different systems: urinary, digestive, pulmonary, neurvous, etc.), chronic  and inflammatory disease that affects 1 to 2 women* out of 10. Worldwide, the average diagnostic delay ranges from 7 to 12 years.


According to the most widely accepted scientific theory, endometriosis can begin as early as the first menstruation, through what is known as retrograde menstruation (Sampson’s theory). However, alternative research suggests that in some cases the disease may originate much earlier in life, potentially during embryonic development, based on the Müllerian embryonic remnant theory.


I share these different hypotheses to highlight the complexity of endometriosis and the fact that science is still working to fully understand its origins. Research in this field is advancing, but it remains incomplete. We will need further studies (and patience) before having clearer and more definitive answers. However, endometriosis is increasingly regarded as a multifactorial disease, involving genetic, hormonal, immune, inflammatory, and potentially bacterial and environmental factors, a complexity we will explore further below.


Because this disease is hormone-dependent, without proper management from the very first symptoms, it can be progressive and cause significant pain and/or short- and/or long-term complications.


Although we mainly refer to endometriosis here, this also includes adenomyosis, often described as the “little cousin” of endometriosis. While closely related, it has some specific characteristics, as well as slightly different symptoms and diagnostic approaches. We can talk about it together.

*Laura intentionally alternates between the terms “women” and “individuals.” While endometriosis predominantly affects cisgender women, Laura is aware that the condition can also affect people who identify as FINTA, an acronym referring to women, intersex, non-binary, trans, and agender individuals. For Laura, inclusive language is important. It allows her to acknowledge both the biological reality of the disease and the diversity of people who may be affected by it.

To properly understand endometriosis, we must first understand how a human body with a uterus functions.


Throughout the menstrual cycle (a menstrual cycle begins on the first day of the period and ends on the first day of the next period; it lasts on average 28 days, although this can vary from one body to another), the endometrium (the tissue that lines the inner wall of the uterus, you can think of it a bit like wallpaper covering the inside of your uterus) gradually thickens throughout the cycle in order to welcome a potential embryo (in other words, a possible pregnancy).


If, at the end of the cycle, fertilization has not occurred, then the endometrium (which is the “nest” where the embryo would normally implant) is no longer needed and naturally breaks down through bleeding. This is what we more commonly call a period.

In principle, this process repeats itself every month until menopause.

In individuals with endometriosis, cells similar to the endometrium migrate…

By being drawn up through the Fallopian tubes, these cells then escape through the space between the end of the Fallopian tubes and the ovaries, as this space is not completely sealed, and they subsequently implant outside of their usual place, which is supposed to be the uterus (these cells can therefore implant on the reproductive system, the urinary system, the digestive system, the pulmonary system, etc.), and this is what we refer to as endometriosis.


However, there is another form of endometriosis called adenomyosis. In this specific case, these cells can infiltrate the myometrium (which is the uterine muscle, therefore inside the uterus), and this is referred to as adenomyosis, in other words, the cousin of endometriosis.


These endometrium-like cells become lesions, implants, or nodules of endometriosis and are most often located in the lower abdomen: on the peritoneum (which is a membrane covering the abdominal organs), on the ovaries, on or within the intestine or the bladder, more rarely on other organs (diaphragm, pleura, lungs), but also on the nervous system (non-exhaustive list).


There is  no organ where endometriosis has not been found… It’s incredible, isn’t it?

This theory is the most widely accepted scientifically, but it has become increasingly controversial over the years as new discoveries emerge.


Indeed, the theory of retrograde menstruation was first introduced by John A. Sampson as early as 1921. This theory helps explain the asymmetrical and seemingly random distribution of lesions, which predominantly occur in the posterior compartment of the pelvis and mostly on the left side.


However, this theory clearly does not explain many forms of endometriosis, particularly those located in extra-pelvic sites.


Further research are therefore necessary, and we will need to remain patient as science continues to investigate and refine our understanding of the disease.


Note: All factors that promote retrograde menstruation (early menarche, short menstrual cycles, heavy menstrual bleeding, menorrhagia, etc.) increase the risk of endometriosis.

Therefore, other hypotheses and research avenues exist that may help explain endometriosis.

Genetic / hereditary factors

There is a fivefold higher risk of developing endometriosis among first-degree relatives (for example, from a mother to her daughter) compared to the general population. In addition, certain genetic variants play either a facilitating or an inhibitory role in the development of endometriosis.

Metaplastic factors

Endometriosis may occur when a generic tissue transforms into a specialized tissue in a location different from where it is normally supposed to be. Theories include:

  • Coelomic metaplasia
  • Hormonal or immunological factors
  • Remnants of the Müllerian ducts
  • Stem cell differentiation

Metastatic theory (transplantation / induction theory)

During menstruation, various blood or lymphatic vessels may draw endometrial cells into the circulation, allowing them to spread throughout the body.

Autoimmune hypothesis

Numerous abnormalities of the immune system have been identified in individuals with endometriosis, although no endometriosis-specific antibodies have ever been clearly demonstrated.

Infectious hypothesis

A recent discovery suggests a potential pathogenic role of bacteria from the genus Fusobacterium in the development of ovarian endometriosis (with possible antibiotic treatment). In addition, correlations have been observed between imbalances in the vaginal microbiome and the onset of endometriosis.

Environmental hypothesis:nvironnementale

One hypothesis considers the role of exposure to certain toxic substances or pollutants (particularly endocrine disruptors), potentially even in utero (that is, while we are still developing inside the uterus before birth).

All of this may seem complex. We said we would keep things simple here and that remains the goal.

But unfortunately, it is difficult to simplify what science itself has not yet fully clarified.



For deeper discussions or tailored explanations,

Laura can address your questions during a consultation or event.

Regarding the types of endometriosis, there are three main forms:

Note: It is important to understand that there is no correlation between the type or stage of endometriosis and the intensity of pain.

One can have a “very small” superficial stage 1 endometriosis and experience an extremely disabling quality of life due to the pain and/or symptoms it may cause.

Likewise, one can have a “severe” deep stage 4 endometriosis and experience no pain at all.



However, in order to better understand the extent of the disease (but again, not the level of pain!), two classifications exist: the type and the stage of endometriosis.


TW: By hovering over the magnifying glass icon, surgical images will appear.

01

Superficial (peritoneal) endometriosis:

on parle d’endométriose superficielle lorsque les lésions restent en superficie, à la surface du péritoine (membrane qui recouvre les organes de la cavité abdominale) . Elles peuvent prendre la forme de kystes (de quelques millimètres à quelques centimètres) en surface des tissus.

02

Ovarian cysts (endometriomas)

Endometriosis is considered ovarian when one or more endometriotic cysts develop on the ovary. These are referred to as endometriomas, also known as “chocolate cysts,” because they are cysts filled with old, coagulated blood whose color gradually turns dark brown, similar to chocolate.


This type of endometriosis directly affects the ovarian reserve and therefore has a more direct impact on the patient’s fertility.

03

Deep endometriosis (DIE)

Endometriosis is considered deep or infiltrating when lesions extend more than 5 millimeters beneath the surface (as opposed to superficial endometriosis) and more specifically when they involve the muscular layer of the abdomino-pelvic organs.


The endometrial-like tissue becomes fibrotic, forming nodules that can infiltrate the affected organ. Deep endometriosis primarily affects: the bladder, the ureters, the digestive tract (rectum, sigmoid colon, appendix), the uterosacral ligaments, and the posterior vaginal fornix (non-exhaustive list).

Endometriosis is classified into four stages:

This staging classification was established by the American Fertility Society (AFS) in 1979 and has been revised since 1985. It is referred to as the AFS score and is determined based on the size and location of the lesions.

It is therefore a purely descriptive classification and is mainly used as a surgical reference and an indicator of fertility prognosis. It is in no way related to the intensity of pain.


This stage can only be determined after surgery. In practice, the surgeon must count the number of lesions, assess where they are located, evaluate their size and their depth, and assign a score accordingly.

Each lesion is scored individually, and these scores are then added together to obtain a total score, which ultimately determines the stage of the disease.

01

Minimal

The stage is defined as Minimal when the score ranges from 1 to 5.

02

Mild

The stage is defined as Mild when the score ranges from 6 to 15.

03

Moderate

The stage is defined as Moderate when the score ranges from 16 to 40.

04

Severe

The stage is defined as Severe when the score is above 40.

So...

why can endometriosis be painful?

The pain associated with endometriosis can be intense and varies greatly from one person to another. It is influenced by multiple physiological and anatomical factors.


Several mechanisms contribute to this complex symptom profile. Inflammation caused by endometriotic lesions plays a central role, as these lesions release inflammatory mediators that can irritate surrounding tissues. Muscle spasms, particularly in the pelvic floor, may also develop as a protective response to chronic pain. The location of the lesions is another key factor: lesions infiltrating sensitive structures such as ligaments, the bowel, the bladder, or near nerves can generate significant discomfort.


Hormonal activity further contributes to symptoms. Because endometriotic tissue remains hormonally responsive, it can react to cyclical hormonal fluctuations, leading to repeated inflammatory processes and pain over time.


In addition, research increasingly highlights the role of nervous system sensitization. Persistent inflammation and repeated pain signals may lead to peripheral and central sensitization meaning the nervous system becomes hypersensitive. In this state, pain can be amplified, prolonged, or triggered by stimuli that would not normally be painful.


It is important to remember that every case of endometriosis is different, and every pain experience is unique. And yet, around 10% of individuals living with endometriosis report no symptoms at all, and we still do not fully understand why.


There is still much to uncover about endometriosis, and many scientific questions remain unanswered.

Endometriosis: Debunking Common Myths

  • A hysterectomy cures endometriosis

    FALSE. 


    While a hysterectomy can be effective in treating adenomyosis by removing the affected uterus, it does not cure endometriosis.


    Endometriosis can persist because it involves, among other mechanisms, the growth of endometrium-like tissue outside the uterus (in areas such as the ovaries, the Fallopian tubes, nerves, the digestive, urinary, or pulmonary systems, and other parts of the pelvis).


    In addition, nerve endings may be altered or damaged by endometriosis, leading to what is sometimes referred to as “pain memory,” a condition in which pain signals can persist even after lesions have been treated and even after menopause.


    Therefore, even after a hysterectomy, endometriosis-related symptoms may persist. Moreover, the disease may continue to evolve, especially in light of emerging scientific hypotheses indicating that its causes are multifactorial and not limited to retrograde menstruation alone.


    Moreover, a hysterectomy carries risks, including surgical complications, hormonal side effects, and psychological impacts. This decision should be made in an informed and thoughtful manner, in consultation with healthcare professionals who are specialized in endometriosis, and after carefully considering all available treatment options in line with your personal choices and goals.


    It is your body. It belongs to you. But it is important to understand that no, a hysterectomy is not a miracle solution for endometriosis (because there is, in reality, no miracle solution for endometriosis...). 

  • You cannot be pregnant if you have endometriosis

    Contrary to the widespread belief that endometriosis prevents any possibility of pregnancy, many people living with endometriosis are able to conceive  (around 60%).


    Endometriosis can contribute to infertility, but infertility is not the same as sterility. Approximately 40% of individuals with endometriosis may experience fertility challenges, yet this does not mean pregnancy is impossible.


    While endometriosis can affect fertility due to lesions, adhesions, and chronic inflammation, it does not systematically cause infertility. Fertility in endometriosis is not only about ovarian involvement. It is a whole-body consideration.


    Pain during intercourse may reduce the frequency of sexual activity. Inflammation may affect the quality of the endometrium and implantation. Tubal permeability can be compromised. Ovarian reserve may be altered. Immune and inflammatory factors may also play a role.


    In other words, fertility and endometriosis involve complex and interconnected mechanisms , not just the ovaries.


    With appropriate medical management, individualized care, and, when necessary, assisted reproductive technologies, many people living with endometriosis are able to carry a pregnancy.


    The path is not always the one that was dreamed of  but many find their own way forward. And for those who do not, we hold space for them with compassion, love, and full solidarity.

  • Pregnancy cures endometriosis

    While some individuals may experience temporary relief from symptoms during pregnancy due to hormonal changes and the absence of menstruation, pregnancy does not cure endometriosis.


    Symptoms can return after childbirth, and the disease may continue to progress over time.


    It is essential to understand that managing endometriosis requires ongoing medical follow-up, individualized treatment, emotional support, and a clear understanding of what is happening in your body during this phase.


    It is also important to acknowledge that pregnancy does not always bring relief. Some individuals may experience significant pain during pregnancy, particularly when existing lesions are present. As the uterus expands and the baby grows, pressure on affected areas can sometimes intensify discomfort.


    However, appropriate medical care and supportive programs can help manage these symptoms and improve quality of life during pregnancy.


    If pregnancy brings relief, (I truly hope it does) but it should never be presented as a treatment or a cure for endometriosis.

  • Endometriosis only affects women of reproductive age

    Contrary to the common belief that endometriosis only affects women of reproductive age, the reality is far more complex.


    Research has identified endometriosis-like tissue in fetuses, and cases of endometriosis have also been reported in cisgender men undergoing high-dose estrogen therapy as part of prostate cancer treatment. These findings suggest that endometriosis may affect a broader range of individuals than previously assumed.


    For this reason, Laura intentionally adopts inclusive language. While endometriosis predominantly affects women, she recognizes that it can also concern people who identify as FINTA (women, intersex, non-binary, trans, and agender individuals).


    In addition, the belief that endometriosis systematically disappears after menopause is incorrect. While symptoms may decrease for some individuals due to hormonal changes, this is not always the case. Persistent symptoms can continue to impact quality of life even after menopause.


    If you would like to explore this topic further, you are invited to read the dedicated myth on menopause and endometriosis.

  • Endometriosis only causes pain during menstruation

    Endometriosis can cause chronic pain throughout the entire menstrual cycle.


    Individuals living with endometriosis may experience pelvic, abdominal, or lower back pain, as well as pain during sexual intercourse, urination, or bowel movements, independently of their menstrual periods.


    Reducing endometriosis to “period pain” contributes to the harmful misconception that symptoms occur only a few days per month. In reality, pain can be persistent and chronic, extending far beyond menstruation.


    This is also why introducing a “menstrual leave” policy is not as simple as it may seem, for multiple reasons , including the fact that endometriosis-related symptoms are not limited to menstruation and may fluctuate unpredictably throughout the cycle.


    Some individuals may experience pain peaks during their periods, while others may not feel increased pain during menstruation at all.


    Every body is different.

    Do not compare your experience to someone else’s.

  • Menopause cures endometriosis

    Endometriosis does not automatically disappear overnight with menopause. While declining hormone levels may reduce symptoms for some individuals (and the absence of menstruation can indeed bring relief) endometriosis can persist after menopause.


    It is commonly stated that the progression of endometriosis tends to slow down or stabilize with menopause. However, this information should be interpreted cautiously. Research continues to evolve, and because endometriosis is a complex and multifactorial disease, there is still much we do not fully understand.


    Even if the progression of the disease is hormonally influenced, symptoms such as pain may persist and still require ongoing management.


    In particular, nerve endings that have been altered or damaged by endometriosis can contribute to what is sometimes referred to as “pain memory,” where pain signals continue even after menstruation has ceased.


    On a more hopeful note, for some women, menopause can significantly reduce endometriosis-related symptoms.


    Each case is unique. It is essential to consult a qualified healthcare professional to assess and manage symptoms individually after menopause — or to prepare proactively for this transition.

  • Endometriosis is, among other things, a psychological condition

    Endometriosis is not “in your head.” It is in your body.


    Endometriosis is a complex gynecological and multi-systemic medical condition with distinct physiological mechanisms.


    While chronic pain associated with endometriosis can have psychological consequences — affecting quality of life, mental health, and emotional well-being — the disease itself is not the result of an underlying psychological issue.


    It is essential to recognize endometriosis as a serious medical condition that requires proper evaluation, evidence-based management, and care from healthcare professionals specialized in the disease.

  • A program, a coach, or a medication can cure your endometriosis

    C'est FAUX. 


    Si une solution miracle existait pour guérir l'endométriose, tout le monde le saurait. 


    Nous profitons de cet encadré pour te mettre en garde contre les coachs, programmes et autres méthodes qui prétendent guérir l'endométriose en quelques semaines ou mois. Jusqu'à preuve du contraire, l'endométriose ne se guérit pas, mais elle peut se soigner. Cela signifie que les symptômes peuvent être atténués, mais la maladie elle-même ne peut pas être totalement éradiquée. 


    Sois prudent.e et consulte toujours des professionnel.le.s de la santé qualifié.e.s pour obtenir des conseils et des traitements fondés sur des preuves scientifiques.


    Bien sûr, tu peux essayer des méthodes qui n'ont pas (encore?) de preuve scientifique, mais on te conseille de faire très attention à ce que tu trouves sur internet et de ne pas accorder ta confiance à n'importe qui. 


    Ta santé est précieuse. 

  • A teenager is too young to have endometriosis

    “You’re too young to have endometriosis.”

    That’s false.


    Contrary to what many people believe, you are not too young to have endometriosis. Your daughter, your sister, your cousin , they are not too young either.


    In fact, a Belgian study (source: UZ Leuven) shows that in Belgium there is an average diagnostic delay of 12 years for adolescents with endometriosis. That says a lot, doesn’t it?


    In reality, endometriosis can affect people of all ages, including teenagers. Medical imaging such as MRI and ultrasound often shows fewer visible signs in younger patients because they are more likely to have superficial forms of endometriosis.

    (and to be clear: superficial does not mean less painful.) These forms are simply more difficult to detect with imaging.


    This does not mean that endometriosis is not present, and thinking so can be counterproductive. In fact, the earlier endometriosis is diagnosed, the sooner we can act to slow its progression or better manage the disease.


    Listen to your body, and don’t hesitate to consult a healthcare professional if you are experiencing symptoms.


    If your pain disrupt your daily life, it is not normal.

  • Artificial menopause is a miracle solution for endometriosis.

    That’s false.


    Contrary to what some people may believe, artificial menopause is not a miracle solution for endometriosis.


    It can sometimes be used as a short-term treatment with very specific medical indications, but it is generally not a long-term solution because of its potential side effects.


    Artificial menopause works by blocking hormone production at the level of the hypothalamus and the pituitary gland in the brain, which interrupts the hormonal signaling to the ovaries and stops the menstrual cycle.

    This mechanism is different from that of the contraceptive pill (even when taken continuously), which works by maintaining stable hormone levels to prevent ovulation without inducing a menopausal state.


    Possible side effects (which can vary from person to person) may include symptoms similar to those experienced during natural menopause, such as hot flashes, mood swings, sleep disturbances, decreased libido, and vaginal dryness. In addition, there is an increased risk of osteoporosis due to reduced bone density.


    It is therefore important to discuss all treatment options with a healthcare professional in order to find the approach that is most appropriate for your individual situation.