Endometriosis May Be Causing Women to Become More Sensitive to Pain

This is the first study that shows a possible relationship between central pain processes and the concentration of cell signaling molecules found in the peritoneal fluid of women with endometriosis

Key Points

Highlights:

• An increase in the concentration of some cell signaling molecules in the peritoneal fluid could be related to hypersensitivity to pain.

Importance:

• This is the first study that provides evidence of a possible link between central pain processes and the concentration of cell signaling molecules and growth factors in the peritoneal fluid of women with endometriosis.

 What’s done here?

• Researchers subjected 11 women with endometriosis and chronic pelvic pain to electrical stimulations to measure their pain perception, which was evaluated using four different questionnaires, namely the Beck Depression Inventory, State-Trait Anxiety Inventory, Catastrophizing Scale of the Coping Strategies Questionnaire, and Short-Form 36.  
• They also collected peritoneal fluid from the women and measured the concentration of 15 different cell signaling molecules and growth factors. 

Key results:

They found that there is an association between the concentration of specific cell signaling molecules and altered central pain processing. More precisely:

• The higher the level of osteoprotegerin (OPG), the higher the magnitude of central pain sensitivity.
• The higher the concentration of TNF-alpha, the higher the magnitude of central hyperexcitability.
• The higher the concentration of glycodelin-A (PP-14) and ficolin-2 lectin, the higher the alteration of central pain processing.  

Limitations of the study:

• The researchers only analyzed a low number of samples of peritoneal fluid.
• Less than half of the 15 different cell signaling molecules and growth factors analyzed showed a significant association with central pain processes. So, this could partly be the result of chance.
• The analysis was not corrected for multiple comparisons, meaning that it might have produced false-positive results.

Lay Summary

Inflammation caused by endometriosis may be changing the way a woman perceives pain, found a new study published in the journal Regional Anesthesia and Pain Medicine.  

According to Dr. Neziri Alban at University Hospital of Bern, Switzerland and the co-authors of the study, cell signaling molecules called cytokines that are produced in the endometrial environment could act as a mediator between the lesions and the changes in pain processing mechanisms in the brain and spinal cord.

It was already known that chronic pelvic pain caused by endometriosis makes the central nervous system more excitable leading to more pain.However, it was not know how endometrial lesions lead

to heightened sensitivity to pain. The relationship between central hypersensitivity and the inflammation of peripheral tissues was also unclear. 

The researchers thought that cell signaling molecules produced in the peritoneal fluid (the liquid made in the abdominal cavity which lubricates the surface of the tissue that lines the abdominal wall and pelvic cavity) could be related to sensitivity to pain.

In order to test their hypothesis, the scientists analyzed 11 endometriosis patients, ages 18 to 37,  experiencing chronic pelvic pain.

Women were subjected to electrical stimulations and then asked to complete four different questionnaires to determine the intensity of the pain they experienced at the time of testing and the highest intensity of pain they ever experienced.  

The researchers also collected peritoneal fluid from the women to determine the concentration of 15 different cell signaling molecules, and growth factors.

They found that an increase in the concentration of some cell signaling molecules in the peritoneal fluid correlated with an amplified central pain processing.

According to the authors, this is the first study that provides evidence of a possible association between parameters of central pain processes and the concentration of cell signaling molecules and growth factors in the peritoneal fluid of endometriosis patients.

Further studies with larger sample sizes are needed to confirm these findings.