Is This The Part Of Endometriosis Treatment We’ve Been Missing?

Endometriosis affects more than 10% of reproductive-aged women, roughly 190 million people worldwide, yet so much is still unknown about the condition.

One of the most frustrating aspects of endometriosis is that your pain often doesn't match what doctors see. Some people with lots of tissue growth and lesions around the uterus report minimal discomfort, while others with barely visible tissue growth experience debilitating symptoms that disrupt their lives.

This mismatch has puzzled researchers and left many patients feeling dismissed or misunderstood for years, but a new study offers an explanation.

The disconnect in endometriosis pain, explained

Endometriosis is a condition that causes cells that mimic uterine tissue to grow outside the uterus. This tissue growth creates lesions that lead to pain during the menstrual cycle, ranging from mild to extreme. Some women with a significant amount of tissue outside the uterus have laparoscopic procedures to remove it, but this doesn't always help to relieve pain.

According to a new study led by Kanako Hayashi at Washington State University, this is because repeated menstrual cycles may do more than trigger endometriosis pain. The research found that recurring inflammation linked to the disease can make the nervous system more sensitive, driving pain that persists even after lesions are removed.

"Once the system is sensitized, the brain keeps responding, even if the original lesions are gone," Hayashi explained in a press release.

This means endometriosis pain isn't just coming from the tissue growing outside your uterus. It's also comes from changes in how your brain and nervous system process pain signals overtime.

How repeated cycles "turn up the volume" on pain

To understand why endometriosis creates chronic pain, Hayashi's team designed a mouse model that mimics what actually happens in a woman's body over time.

Most previous research induced endometriosis-like conditions only once. But Hayashi's group introduced multiple cycles, simulating the repeated buildup of menstrual tissue (called retrograde menstruation) that's thought to contribute to the disease.

The researchers found that mice exposed to repeated cycles showed heightened sensitivity and lasting changes in the nervous system. Inflammation increased in the pelvic region, and signals traveled along nerve pathways to the spinal cord and brain, where researchers observed clear signs of neuroinflammation.

"That repeated stimulation acts like turning up the volume again and again," Hayashi explained. "Eventually, the system becomes hypersensitive. Even small signals can feel very painful."

This helps explain why pain can persist long after lesions are surgically removed. Once the brain's pain-processing circuits are sensitized, they can continue to generate pain signals independently, regardless of what's happening in the pelvic region.

"It becomes a feedback loop," Hayashi said. "The body is sending signals to the brain, and the brain is reinforcing those signals back to the body."

What this means for treatment

The study also points toward new approaches for managing endometriosis pain. Rather than focusing solely on removing tissue or suppressing hormones, therapies could target inflammation in the nervous system itself.

In the study, both a commonly used hormonal drug and an immunomodulating compound reduced pain sensitivity and brain inflammation in the mouse model, even without shrinking the lesions. This suggests that addressing neuroinflammation directly could provide relief for people whose pain persists despite conventional treatment.

"We now have a system where we can follow the entire process from the beginning," Hayashi said. "That gives us a powerful way to develop better treatments and, hopefully, detect the disease earlier."

The takeaway

For too long, the disconnect between pain severity and visible endometriosis has left women feeling unheard. But this research reveals a biological reason for endometriosis pain that continues despite treatment.

This reframe of endometriosis will hopefully open the door to treatments that address the full picture: not just the lesions, but the brain changes that make the pain so persistent.