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Endometriosis, the invasion of the uterus


Endometriosis is a condition in which tissue from inside the uterus, endometrial tissue, grows. This would not necessarily be a bad thing, except that it grows outside the uterus, in areas of the body where it should not be. Normally this appearance and growth is in the ovaries, the fallopian tubes and the tissue lining the pelvis.

However, it is not limited to these areas. It can appear in the intestines or urinary bladder. Some reported clinical cases also include the liver, the lungs, the sciatic nerve, the heart, the pancreas, the brain… One could almost say that, if such an organ exists, endometriosis can occur.

It is estimated that approximately 10% of women of childbearing age suffer from endometriosis, 190 million people worldwide. In many cases it is asymptomatic and undiagnosed.

One of the problems is that, as the saying goes, “you can take the endometrial tissue out of the endometrium, but not the endometrium out of the endometrial tissue“. Or something like that, there are many sayings. It turns out that the endometrial tissue outside the endometrium still behaves in the normal way, as if it were inside. In each menstrual cycle it thickens, bleeds and sloughs off. But in its new location it has no way out of the body and is trapped inside.

This sloughed tissue causes irritation and inflammation in the surrounding tissues. If it is not fixed and remains chronic, it leads to scar tissue.

It is a disease of mysterious causes, which makes it difficult to prevent and predict. Depending on the situation, there are several hypotheses, which are not mutually exclusive:

  1. As the human body is as wonderful as it is horrible, one option is that menstrual blood travels up the fallopian tubes into the pelvic cavity, rather than being expelled from the body. This is called “retrograde menstruation”. Endometrial cells that were in the blood could adhere to the walls and behave as if they were still in the endometrium.
  2. Another theory holds the possibility that peritoneal cells, proving that there are no limits if you set your mind to it, can transform into endometrial-like cells, due to hormonal and/or immune system effects.
  3. A third theory argues that stem cells from bone marrow and other possible regions can spread through the bloodstream and differentiate into endometrial cells. This theory would explain why you wake up one day and have uterine cells at the other end of your body.
Endometriosis, the invasion of the uterus

On risks and genes

Although the causes are not yet understood, some risk factors are known. Endometriosis is most common during the time between menarche and menopause. High oestrogen levels, long menstrual periods or reproductive tract disorders are also related. And of course, genes, always genes.

Endometriosis is hereditary. A family history of endometriosis is considered a risk factor, not only for the likelihood of developing the disease, but also for its increased severity. We can therefore say that endometriosis is partly genetic.

The risk of DNA changes in endometrial cells is relatively high compared to other tissues in the body. It is one of the fastest growing and most plasticised tissues in the human body, going through about 400 menstrual cycles in a woman’s lifetime.

And it exists in an environment of oxidative stress, coexisting with a microbiome (because in this area of the body there are microorganisms in addition to our cells) and with inflammatory states, often caused by menstruation itself. This tissue has gone through experiences that no one should have to go through. These circumstances increase the likelihood of genetic alterations in the cells.

Some of the genes that have been altered are common to cancer. One study found that the TP53 gene, a well-studied tumour suppressor, was significantly lost in endometriosis tissue when compared to controls. The same has been seen with the PTEN gene, another tumour suppressor.

It has been suggested that the chain of mutations leading to endometriosis follows similar steps to the development of colorectal cancer. This would explain why, although retrograde menstruation is relatively common, endometriosis does not always occur. The cells need to have previously altered cell adhesion and persistence mechanisms to develop the disease once they rise with the bloodstream.

Therefore, people who already have several familial mutations, hereditary endometriosis, are more likely to develop these cells that refuse to die.

To reinforce this hypothesis, it is known that there is a correlation between endometriosis and some cancers, such as ovarian carcinoma.

What happens when you have endometrium where you shouldn’t?

Symptoms of endometriosis include, but are not limited to:

Dysmenorrhoea: pain associated with your menstrual period. Like most pain, its intensity usually correlates with severity, although this is not always the case. Next to infertility, it is considered the most distinctive symptom.

Pain during sexual intercourse. Endometriosis is apparently very puritanical and demure. It will make it difficult for you to have sex.

Hypermenorrhoea: menstrual bleeding is heavier in quantity and lasts longer. There may also be metrorrhagia, vaginal bleeding outside of menstrual periods.

Infertility. It is caused by two main components. On the one hand, the inflammatory state of the sexual organs and the activity of the immune system, which create a negative environment for the oocyte and its fertilisation. On the other hand, the structural alteration of the reproductive organs. Cases of endometriosis have sometimes been found in women who have come to clinics for infertility problems.

Diagnostic methods are also diverse. Non-invasive methods include magnetic resonance imaging and ultrasonography. A more robust method is laparoscopy. In this method, a small camera is inserted into the abdomen to visualise the interior.

Unfortunately, so far no reliable biomarker has been found for the diagnosis of the disease.

It takes years from the onset of endometriosis until the first recognisable symptoms appear. It is suspected that most begin during adolescence, during the first menstrual periods and hormonal peaks, which would be diagnosed and operated on between the ages of 24 and 34, the age bracket with the most patients.

With so many theories of its origin and a wide range of symptoms, but not very specific, each case can present a different profile, which complicates diagnosis and detection. As an example, from 1973 to 2021, 22 different classification systems were developed.

Unfortunately, although it is generally a benign disease, with no risk to the patient’s life (there are exceptions, such as the patient who had endometriosis IN THE BRAIN), there is no cure. The usual treatment is palliation of the symptoms, and removal of the lesions by surgery or heat ablations. In 1960 they were already the main cause of surgery in women. During the menopause, the severity of the disease tends to decrease naturally due to the drop in hormone levels.

If you want to see if your endometrial tissue has a genetic predisposition to be adventurous and travel to other regions of the body, you can check it with the tellmeGen Advanced DNA Kit.


Carlos Manuel Cuesta

Graduate in Biology. PhD in Biotechnology

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