Other Proposed Causes for Endometriosis

Are there additional believed causes of endometriosis?

As there is still so much more knowledge and research needed to be done before endometriosis can fully be understood, scientists have put forth a number of theories explaining its believed cause(s). These ideas both connect to other previously proposed theories, and can even stand on their own in some cases.

What is Uterine Peristalsis and how does it relate to endometriosis?

Uterine peristalsis is one of the fundamental functions of the non-pregnant uterus. Peristalsis is the rhythmic contraction and relaxation of tissue muscle that occurs in waves. Contractions of the uterus allow for proper menstruation as regulated by the bodies sex hormones, estrogen and progesterone. It is also involved in early reproductive processes, such as sperm transportation, egg implantation, and even retrograde menstruation. Dysfunctional uterine peristalsis may play a part in the development of endometriosis, particularly through the process of retrograde menstruation. Researchers propose that dysfunctional peristalsis may be the driving force behind retrograde menstruation, and in turn endometriosis development.

Hormones role in the development of endometriosis

Endometriosis is often described as a disease of menstruation and sex hormones are the driving force behind a woman’s ovulation cycle. Researchers, therefore, speculate that these chemicals play a role in endometriosis development. Estrogen and progesterone have been a subject of much debate amongst endocrinologists in all sorts of endometriosis theories, ranging from retrograde menstruation to genetics. The former theorists will state that fluctuations in sex hormone levels can cause dysfunctional uterine peristalsis and retrograde menstruation, while scientists favoring the genetic approach can state that abnormal gene expression cause irregular levels in sex hormones and lead to endometriosis. More research is needed to fully understand the exact role of estrogen and progesterone in the development of endometriosis.

Female sex hormones are regulated in the menstrual cycle
Female sex hormones are regulated in the menstrual cycle. Since endometriosis is a disease of menstruation, the role these hormones play in the development of endometriosis is a highly discussed subject.

The role surgery can play in aggravating endometriosis

While surgery is the only definitive way to both diagnose and treat endometriosis, it must be approached with care. This is because surgery always presents the risk of complications. Excision surgery is the gold standard for relieving endometriosis symptoms, and ensures a safe and effective method for patients, with minimal complications. Despite this, some surgeons still use other surgical techniques such as ablation and fulguration. Although these methods aim to destroy suspected endometriosis lesions, they can lead to complications as they use a large amount of energy and heat. They often aggravate lesions or harm surrounding healthy tissue. Patients should therefore pick a surgeon with care and ask the surgical methods used to destroy endometriosis lesions.

The Lymphatic system’s role in endometriosis development

The lymphatic system is part of the circulatory system and is responsible for carrying and removing fluids from the body’s tissues. This fluid can contain a variety of essential life components, including red blood cells, white blood cells, and plasma. The lymphatic system is known for being what is called an “open” system. Many have proposed that the blood network of this system plays a role in transporting endometrial cells to other parts of the body, which explains how endometriosis can spread throughout the body. The lymphatic system also serves as a connection for endometriosis involvement with the immune system.

Endometriosis involvement with the lymphatic system
Endometriosis involvement with the lymphatic system is one proposed idea for how the disease can spread throughout the body.

Could there be an immune component to endometriosis development?

The immune system is responsible for protecting the body from disease. In endometriosis, the peritoneum (lining of the abdomen) and vital organs such as the intestines, ureter, etc. become excessively red and swollen. Because an inflammatory response typically occurs when the body is fighting an infectious disease, the immune system’s role in endometriosis progression has become a subject of much interest. Researchers suspect that an issue in the immune system may make the body ill-equipped to recognize and destroy endometrial tissue growing outside of the uterus. For example, some have noted decreased activity of natural peritoneal killer cells, which are responsible for destroying harmful pathogens in the body, in women suffering from endometriosis. Whether this is due to a hormonal change, genetic component or some other factor still needs to be seen. Nevertheless, all of this information is key in ultimately determining the immune system’s role in the underlying cause of endometriosis.

Oxidative Stress and Endometriosis

Free radicals are highly reactive molecules of oxygen. Typically, the body will manage these molecules with anti-oxidants. Although some free radicals can be beneficial for the body, an excessive amount of reactive oxygen can lead to oxidative stress (OS), which can be harmful. The elevation of free radicals in the peritoneum (lining of the abdomen), and lack of anti-oxidants, is suspected to be one of the links in the chain of events causing endometriosis. This could help explain how endometriosis continues to grow and spread throughout the pelvic cavity, due to the high reactivity of these radicals. This could also lead to DNA damage in endometrial cells and excessive inflammation and tissue damage.

Oxidative stress from an abundance
Oxidative stress from an abundance of free radicals over anti-oxidants can lead to inflammation and tissue injury, both hallmarks of endometriosis.

Apoptosis suppression and alteration of cell fate in endometriosis

Apoptosis occurs when the body signals out dysfunctional cells which could be harmful and destroys them. This is a highly regulated mechanism and is key in the body’s maintenance of preventing disease. In fact, the malfunction in the mechanisms regulating apoptosis is a common cause of cancer. As the body cannot rid itself of harmful, damaging cells, these cells grow and spread, causing tumors and cancer.

Endometriosis cells have the capacity to avoid apoptosis. The role this plays in the development of the disease is currently being investigated and can be linked to genomics through the upregulation (increased expression) of genes coding for anti-apoptotic factors and the downregulation (decreased expression) of genes coding for factors promoting apoptosis. These are similar studies to those oncologists perform when studying the mechanisms of specific cancers, and some gynecologists have proposed a link between endometriosis and certain cancers regulated by the female sex hormones - breast and ovarian cancer. However, there is limited conclusive evidence revealing the nature of this relationship and further research is needed.

References

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  4. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3204940/
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  8. https://www.ncbi.nlm.nih.gov/pubmed/16820124
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