Many patients with endometriosis are being prescribed opioids and not enough people are aware, not even physicians.

It first dawned on doctor Georgine Lamvu at a national conference for gynaecologic surgeons. As a specialist in chronic pelvic pain, she and her colleagues were conversing about the pros and cons of doing multiple repeated surgeries for those with endometriosis.

'Endo', as it's sometimes shortened, is a little-known, often painful disorder that occurs when endometrial-like cells grow outside the womb. Sometimes referred to as 'the most common disease you've never heard of', it impacts no less than 1 in 10 women and is one of the top three causes of female infertility worldwide.

Today, there is still no cure or long-term treatment for endometriosis; in many cases, surgeries are repeated with little to no relief. A potential drawback to this approach, Lamvu remembers saying at the conference, is that a lot of patients end up taking opioids.

"A surgeon blatantly said to me, 'Oh, that's not true. We don't use opioids to treat patients with endometriosis,'" Lamvu told ScienceAlert.

"And I said, 'Oh, well that's interesting. Why don't I try and find out.'"

It wasn't so much a hunch, she says. Lamvu knew for a fact that opioids were commonly used to treat chronic pain patients outside her own practice, even though regulations were now stricter.

Over the years, opioids have become one of the most common treatments for chronic pain in the US. And while they might be useful for short and acute cases, their efficacy in the long run is currently under intense scrutiny.

Today, despite scientific evidence suggesting opioids are ineffective at treating chronic pain, 92 percent of physicians and patients believe these drugs help reduce pain and 57 percent report a better quality of life.

When as many as 19 percent of those who are prescribed long-term opiates abuse the drug or become addicted, it's no surprise that many chronic pain patients are wrapped up in the opioid crisis.

"It almost seemed inconceivable to me that endometriosis patients with chronic pelvic pain would somehow be spared the opioid epidemic," Lamvu told ScienceAlert.

"It just didn't really make sense, even though it's what this colleague of mine was saying."

Her deep dive into the issue, published in Obstetrics & Gynecology in June this year, confirmed her worst suspicions: too many people with endometriosis have been taking prolonged opioids for their chronic pain. To her knowledge, it's the largest sample size to date, drawing on publicly available insurance data from 53,847 endometriosis patients and 107,694 others without the disease.

From 2006 to 2016, Lamvu and colleagues found women with endometriosis were nearly three times as likely to fill an opioid prescription compared to the control group. And while Lamvu admits she has no evidence any of these patients are addicted or dying from narcotics, she sees the pattern as a big problem.

In the findings, patients with endometriosis were nearly four times as likely to fill a larger dose of opioids, equivalent to some 100 milligrams of morphine or more. According to the US Federal Drug Administration (FDA), that's a large enough amount to cause an overdose if taken by someone who isn't regularly taking opioids.

The data also reveals that these patients, aged anywhere between 18 and 49 years, are more likely to use opioids for over a month and at the same time as benzodiazepenes - a combination that is 10 times more likely to lead to a fatal overdose.

Similar results were found even after excluding prescriptions specifically for surgery.

"I was surprised by the magnitude of the numbers, I can't lie about that," Lamvu admits. "I thought we would see a difference but I just didn't think it would be this."

The prescriptions appear to start straight away. Within seven days of being diagnosed with endometriosis, her team found more than a quarter of endo patients filled an opioid prescription.

The results are consistent with a 2018 survey from the American College of Obstetricians and Gynecologists (ACOG) that found almost a quarter of ob-gyns nationwide were prescribing opioids to patients with endometriosis.

While there's some other research out there looking at chronic pelvic pain and opioid rates, Lamvu and her team's study is one of the first to look at endo specifically.

"Although these well-insured study participants may not represent the entire US female population, their prolonged opioid use despite evidence of little or no therapeutic benefit is astonishing," writes reproductive endocrinologist Robert Rebar from Michigan State University in a review of the team's study.

People with endometriosis might very well be hidden figures in the opioid epidemic; we just don't have the data to say for sure. And much of what we do know is anecdotal.

In his decades of experience treating gynaecologic diseases, Serdar Bulun from Northwestern University told ScienceAlert he has seen at least two or three high school age teenagers who were addicted to opioids when they came to him and who had been using these narcotics for a year or more.

He himself does not prescribe opioids for chronic pelvic pain, and he suspects these patients were first given the drugs in an emergency room. A good number, he says, go to the local hospital when they experience intense pelvic pain, usually because they can't get in to see their gynaecologist right away.

In these urgent situations, doctors might see a narcotic as the only option. Encouraged by the pain relief, patients might later go to their regular doctor and ask for more, he suggests.

"I presume it must be an issue," Bulun told ScienceAlert. "I don't know what the magnitude is."

One young patient, he recalls, was on such strong pain killers, she was finding it hard to concentrate in her high school class. And yet, in the end, nothing else was helping her cope.

That's the saddest part for Lamvu: the sheer lack of alternatives for desperate patients and for physicians who desperately want to help. As an expert on pelvic pain, she laments the fact we've spent two or three decades on one class of pain medication at the expense of further research on such a common pain disorder.

Today, for the average endo patient, arriving at a diagnosis takes more than four years; by that time, all a person wants is some sort of relief.

"We've done a disservice to our patients, because we've basically said, 'Well, you need a surgery. And then if that doesn't work, pain management. And if that doesn't work, then opioids.'"

Sawsan As-Sanie, a chronic pelvic pain specialist at the University of Michigan, is now building on Lamvu's findings. Her research has not yet been published, but she told ScienceAlert that her preliminary results suggest a very high prevalence of opioid prescriptions are being given to patients with endometriosis.

A large portion of these are not related to surgery, and a small but worrying subset of patients are taking prolonged high doses.

"I'm not necessarily surprised because it's frankly not different to what we see in other chronic pain populations," As-Sanie told ScienceAlert, "but I think it does bring light to the fact that even amongst patients where we have an identifiable cause for their pain, they are still being prescribed opioids that we know can be very dangerous."

Few healthcare providers are adequately trained to diagnose or manage endometriosis, she says, and far fewer take the time to properly educate their patients about pain management or set their expectations - even though a recent study by her team has actually shown that such information can decrease opioid use after hysterectomies.

In 2017, ACOG reported that up to "63 percent of general practitioners feel uncomfortable diagnosing and treating patients with endometriosis, and as many as half are unfamiliar with the three main symptoms of the disease." In another study, published that same year, some clinicians were found to be so ill informed, they thought endometriosis was caused by poor mental health.

As such, As-Sanie urges those with endometriosis to work with their primary care physicians and find a gynaecologist who listens to their concerns and fully understands all the available options, whether medical, surgical or pharmacological.

There's not just one treatment that fits all, she says. And patients deserve safe, effective, non-addictive strategies to manage their chronic pain.

The findings were published in Obstetrics and Gynecology.