Causes & Risks for Endometriosis
Despite an enormous amount of research into the cause of endometriosis, there’s no definite explanation for how it develops! The five theories currently in circulation are:
1. “Retrograde menstruation theory.”
This menstrual theory has been around for over 100 years. It suggests that when the functional layer of the endometrium is shed in a “period”, some of it goes “back” through the Fallopian tubes into the pelvic cavity, where it survives and forms endometriosis.
2. “Coelomic metaplastic theory.”
This embryological theory revolves around a shared origin for the cells that make up the peritoneum and the endometrial cells. The theory is that these peritoneal cells somehow “transform” into endometrial cells, without anyone providing any precise detail of how this happens!
3. “Müllerian remnant theory.”
This is another embryonic development theory. It proposes that some of the cells that form the uterus don’t migrate to their final position but remain in the pelvic cavity and form the basis of future endometriosis. Again there is a lack of detail of how this happens!
4. “Autoimmune dysfunction theory.”
This autoimmune theory suggests that disruptions to normal immune responses drive the development of endometriosis, with the evidence supporting this including:
- A specific tumour necrosis factor type of cytokine (TNF-α-MMP9-SRC-1 isoform) being linked to the development of endometriosis. i
- The early stages of endometriosis have more antibody, white blood cell, and cytokine activity than the later stages of endometriosis. ii
- A low immunity to endometrial antigens (IgG and IgA) correlates to higher rates of endometriosis.
5. Low testosterone levels in the womb and after birth, which alters sexual development and the nature of the Hypothalamus-Pituitary-Ovary (HPO) axis. This is the polar opposite of the problem of elevated prenatal testosterone that women with PCOS face. The research is relatively new, but offers the possibility of new treatments that alter hormone levels, especially aromatase can which turns testosterone into estrogens. ii-iii
While there’s confusion about the cause of endometriosis, the known risk factors include:
- Genetics, with the daughters or sisters of women with endometriosis, have a higher risk of developing it. Women with an affected first-degree relative are about ten times more likely to have endometriosis. iv
- Long menstrual periods (over 7 days of bleeding) increase the risk.
- Short menstrual cycles (less than 28 days) increase the risk.
- Not having children increases the risk, but the disease is linked to lower fertility, which raises the question of which comes first?
- Starting periods before the age of 12 increases the risk.
- Contraception with intra-uterine devices (IUDs) raises the risk.
- Abdominal surgery also raises the risk.
- Excessive exposure to external synthetic or natural chemical compounds that imitate estrogen (xenoestrogens) increase the risk. These include plant estrogens and PCBs as they encourage the endometrium to grow. There are thousands of EDCs (endocrine disrupting chemicals), many of them in beauty products.
- High oxidative stress levels correlate to the development of endometriosis. v
- Low antioxidant levels are connected to endometriosis development. vi
- Endometriosis is found most often in women in their 30’s and 40’s.