TikTok Summaries

Endometriosis is an estrogen-dependent inflammatory condition primarily affecting women of reproductive age.  11% of Australian women have been diagnosed with is, but what is Endo? 

Your reproductive system contains a uterus which houses endometrial tissue. During your menstrual cycle, the tissue builds and grows, if fertilization of the egg doesn't happen this endometrial tissue is shed during menstruation. In endometriosis this endometrial tissue grows in the extrauterine space,  areas such as the fallopian tubes, ovaries, and other tissues within the pelvis (And in rare cases may spread to non-pelvic organs). This endometrial tissue then proceeds to do its normal function of building and shedding but in the wrong area, and this is where complications occur. This process can lead to the development of long-term inflammation leading to scar tissue that can lead to pelvic organs and tissues sticking together. The cause is still unknown but click here to read about the 4 theories.  

The pain associated with endometriosis relates to the inflammatory nature of the disease which causes pain most commonly in the pelvic region. Since endometriosis is estrogen-dependent, and estrogen being a known influence on pain perception, people with endometriosis may experience heightened pain. The decline in fertility is due to inflammation leading to low amounts of tissue damage. In conjunction with tissue damage, there is scar formation (Yep, we can even form scars inside of our bodies!), as the scar ages, it undergoes contracture which is essentially a process of shortening. Meaning it alters the positioning of all the pelvic organs.

    There are many systems we use to classify endometriosis as a disease, the one shown in the video is the ASRM system, which is also called the revises ASF system as was developed by the American Society for Reproductive Medicine. It classifies endometriosis into four stages: minimal, mild, moderate, and severe. This classification system separates cases of endometriosis based on how far the disease has progressed. A patient’s stage is determined by a health professional assessing a series of criteria that score the patient. The lower the score the less severe the progression of the disease. The criteria that are used to score cases are: implants, ovarian cysts, and adhesions. An implant is when the endometrial tissue leaves the uterus and attaches somewhere else in the body where it will continue to grow and bleed like other endometrial tissue (periods), but it will cause significant damage. Larger implants that are deeply set into the place they attach get a higher score. Ovarian cysts are also used as criteria, they are found in more severe cases. What happens here is implants in the ovaries can join together and fill with blood when the lesions bleed, creating a cyst. Larger cysts receive higher scores, having cysts in both ovaries rather than just one also increases the score given. Another criterion used to sort endometriosis stages is adhesions. Adhesions are present in later stages (moderate, and severe). Adhesions are where two organs or two parts of different organs can be joined together, the endometriosis starts a process that creates a product that is like a bridge made of scar tissue between the two surfaces. Adhesions are bad because they can shorten and take the organ that they are attached to with them changing the shape of the site they attached to, a bit like when a draw bridge is raised and lowered. Adhesions can be thin and translucent and filmy, or they can be thick and denser. Adhesions that are denser receive higher scores. The important thing to remember about this system of classifying endometriosis is it doesn’t sort using symptoms, so it is possible to have stage 1 and experience a large amount of pain or have stage 4 endometriosis and not experience any symptoms. If you would like more information here are some articles that explain how the stages present https://www.health.com/condition/endometriosis/endometriosis-stages, and https://www.advancedgynaecologymelbourne.com.au/endometriosis/stages. You are also welcomed to check out any of our mentioned sources found on the references page.

Regurgitation- The regurgitation theory suggests a black flow of menstrual endometrial tissue through the fallopian tubes leading to the implantation of other areas within the pelvic region. Once menstruation ends the cycle begins again, the endometrial tissue begins to perform its normal function of building itself up in preparation for fertilisation, including the process of producing blood vessels to have a rich blood supply. This again may lead to chronic inflammation which can lead to adhesions (Scarring)

Benign metastases theory - Endometrial cells spread via our body’s blood vessels and lymphatics to other areas outside of the pelvis which may include lymph nodes, brain, and lungs.

Metaplastic theory- Cells in the lining of the pelvis and lower abdomen undergo metaplasia (Changing of cell type) into endometrium tissue. This is due to some undetermined cause whether hormonal, infectious, or environmental.

Extrauterine cell theory- Stem cells are cells within our bodies that can turn into a wide variety of different cells. In the extrauterine cell theory, stem cells from bone marrow morph into endometrium tissue in areas that aren't the uterus but surrounding the uterus.

  Endometriosis is an idiopathic disease; this means we do not know exactly what causes it. However, scientists have come up with many theories, explaining how cells from the endometrial lining (what you shed during a period) end up attaching themselves to other parts of the body like ovaries, fallopian tubes, even the pelvis or abdomen. The first theory was presented by John Sampson in 1927. Known as Regurgitation Theory, it is also referred to as implantation theory or transplant theory. He proposed that endometriosis was caused by retrograde menstruation, which is what happens when the endometrial tissue from a period moves up  the fallopian tubes and into the pelvic space, attaching to surfaces. Sampson suggested that the endometrial tissue in the pelvic space would attach and form the abnormal tissue lesions that happen in endometriosis. It is currently the most widely accepted theory on how endometriosis happens. However, at the time people thought it was unlikely as there hadn’t been many cases of retrograde menstruation seen before, and scientists didn’t think that it was very common. It has since been shown to occur in many women. Other theories developed include the Benign Metastases theory, Extrauterine Stem Cell Theory suggesting stem cells differentiate into endometrial tissue and form lesions. and the metaplastic theory proposed by Peter Gruenwald in 1942 where surrounding cells in the pelvic space undergo metaplasia, they become endometrial tissue and form lesions. We do not yet know which if any of these is the correct theory of origin for endometriosis, all have evidence in support and against them, it may be a combination of these factors. For more information, please have a look at our other TikTok on theories of Pathogenesis, and the references provided. 

The interesting thing about regurgitation theory is that it is based around the concept of retrograde menstruation. This is when you have your period a little bit of the endometrial lining you shed actually goes against the flow of gravity and moves out of the uterus into the fallopian tube, and from there ends up in either the pelvic space, ovaries, fallopian tubes, on the outside of the uterus and in some rare cases much more distant locations in the abdomen. Retrograde menstruation actually can happen in both physiologically normal menstruation, and in people with endometriosis. The difference is normally what will happen is the endometrial tissue may only temporarily attach, or not attach at all and it will be cleared by the immune system killing the endometrial cells in a process called apoptosis. In the case of endometriosis, the endometrial cells will attach, they will not be killed by the immune system and as such will form more permanent lesions. These lesions will continue to grow, and they will establish a blood and nerve supply. They will also continue to bleed in a cycle, similar to the endometrial tissue found in the uterus. If you would like to know more, I would recommend the Klemmt & Starzinski-Powitz article, it has a great diagram (figure 1) that summarizes the process. The citation for that article can be found in the reference list.

  When endometrial tissue enters the pelvic region to form a lesion, it will go looking for an area of the pelvic region (peritoneum) that has a damaged basement membrane. The basement membrane is like a sheet that sits in between layers of tissue, when its damaged it is easier for the endometrial tissue to attach and invade forming a lesion. the immune system will try and get rid of any endometrial tissue before it can attach but sometimes the clump of endometrial tissue will be too big for the immune system to kill all of the individual cells before the endometrial tissue can attach. When this happens a lesion forms. Once the lesion has formed it releases a hormone that make the body produce more blood vessels. The new blood vessels will grow around the lesion and it will provide the lesion with oxygen and nutrients that it needs to function. 

   Once endometrial tissue leaves the uterus and enters the pelvic region (also called peritoneum) it will want to attach to the surrounding tissue. If the body is not able to remove the endometrial tissue before it attaches then it will grow into the surrounding area, where it forms what is called an endometriotic lesion. The lesion will create its own blood supply, and cause damage. The body will still be trying to remove the lesion. It does this by activating the immune system, a side effect is the immune system will cause inflammation. The inflammation will make the area swollen and painful. The lesion can also activate sensory nerves which carry signals to the brain which can cause pain. In addition to this, the lesion will also continue to bleed in a cycle much like a period, the bleeding will cause the immune system to stay active and as a result, the area will stay inflamed. This is what makes endometriosis an example of chronic inflammation. The inflammation and the nerve signals will both contribute to the symptom of pain that is common in endometriosis. Interestingly the type and location of the pain will depend on where the lesion has formed, for example, lesions on the ovaries will create different types of pain to a lesion that would form on the bladder.

   One of the more common symptoms of endometriosis is infertility. The disease affects 2-10% of the general population, but in women with infertility, about 20-50% have endometriosis, so endometriosis is represented strongly. What this means is that scientists believe it’s a causal and direct reason why women experience infertility and difficulty having children.  We do not know fully how the disease causes infertility, but currently we think that it is a combination of different factors, including that endometriosis, can change the shape of your pelvis, it can affect hormone function, and also it can affect the function of the area around the uterus, and nearby organs like the ovaries. If you think this could be you it is important to know you have options. As with all pregnancy, younger women tend to have more success conceiving naturally, however, if it is not working there are other options available. Many women with endometriosis have been successful with IVF, and current data suggests that surgery can increase the likelihood of natural conception. If you would like more information on endometriosis Australia has an article on it. https://www.endometriosisaustralia.org/post/2016/12/05/fertility-and-endometriosis-should-i-worry you are also welcomed to check out any of our sources found on the references page. . 

  Pain is often listed as a symptom of endometriosis however pain is a very general term. The specific type of pain felt will be different in each individual case of endometriosis because the type of pain depends on where in the body the endometriotic lesion is found.  

Lesions on the wall of the peritoneum (pelvic cavity) will result in changes to the pelvic anatomic, and general pelvic pain.

Lesions on the Bladder will cause problems with the storage of urine as well as inducing pain when you pee (dysuria), and it can also cause bloody pee (hematuria)

Lesions that form in the ovaries quite often become what is call chocolate cysts, where the lesions will join together, and bleed, which is what gives them that chocolate dark red color. Chocolate cysts will cause symptoms of increased pain during the period, general pain in the pelvic region not during menstruation, and can sometimes cause pain during sex (dyspareunia). 

Other common regions that lesions are found include the pouch of Douglas, the rectovaginal septum, on the surface of the uterus, and the fallopian tubes although lesions in the fallopian tubes are less common because endometrial tissue doesn’t tend to stop in the fallopian tubes it usually keeps moving.

  Endometriosis is a leading cause of pelvic adhesions in women. Because it is a chronic inflammatory disease it can lead to the formation of adhesions. An adhesion caused by endometriosis is when the tissue of the uterus, or peritoneum grows thick bands of scar tissue and connects to other body organs and/or the abdominal wall.  The formation of this scar tissue is the body’s reaction to inflammation. This occurs when the body’s immune system response is activated. What happens in the immune response is the body produces immune cells to fight the endometriosis, it does this by killing the endometrial cells that are causing inflammation. But the immune system can’t remove all the endometrial tissue so the response continues and the inflammation becomes chronic (long lasting).  The side effects of prolonged inflammation include pain and swelling, and the formation of a  fluid with the protein fibrin in it, which in turn leads to granulation tissue a (precursor to scar) formation, when the granulation tissue becomes scarring it pulls tight and the two surfaces it is attached to move closer together. This will affect both structure and function..