The problem with endometriosis research

Women’s reproductive health attracts far less research funding than almost all other medical research. As for endometriosis — a condition that affects around 10% of women of reproductive age — the lack of research is particularly striking. This debilitating condition can impact day-to-day life, education, work, and mental health, but its cause remains unclear, and there is no cure for it. Why is it so underresearched?

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Why is endometriosis still so underresearched? Image credit: Michele Pevide/Getty Images.

“That time of the month,” “shark week,” “crimson tide,” “got the painters in,” “on the blob,” “visit from Aunt Flo,” “the curse” — these are just a few of the many euphemisms for something experienced by 50% of the female adult population: menstruation. But why are there so many? Are we afraid to call it by its name?

Could it be that society’s reluctance to speak plainly about periods is one of the reasons why issues with women’s reproductive health are so underrecognized and underresearched? 

Menstruation

Most females start to menstruate between the ages of 9 and 15. Monthly cycles continue until the menopause, which, on average, happens at around 52 years of age. So most women will have in the region of 450 periods during their life.

For around 20% of women, these are merely a monthly inconvenience. But for more than 80%, they are accompanied by some measure of pain. And for 1 in 4 women, the pain can be severe enough to impact daily life.

We often normalize period pain as “part of being a woman.” For many, mild to moderate pain associated with menstruation can be controlled with over-the-counter pain relief, diet, and exercise.

However, debilitating pain is another matter. Menstrual Matters, a nonprofit online information hub, states that period pain “should not be regularly severe and debilitating.”

If it is, there is likely to be an underlying cause, which may need medical investigation. For pain that persists, occurs in the run-up to periods, and does not respond to pain relief, that cause may be endometriosis.

What is endometriosis?

Endometriosis is “a systemic disease that is often painful and chronic.” Current estimates suggest it affects 176 million reproductive-age women worldwide. 

Symptoms can include:

  • debilitating pain during menstruation
  • excessive bleeding during periods
  • pelvic pain at other times of the month
  • lower back pain
  • pain when emptying the bladder or bowels
  • pain during and after sexual intercourse

In severe cases, endometriosis can cause fertility issues. Some 40% of women with infertility also have endometriosis.

The condition is characterized by the growth of tissue similar to the endometrium, or womb lining, in areas outside the uterus. This tissue — endometrial lesions — commonly grows in the following areas, though it can also infiltrate other parts of the body, such as the:

  • ovaries
  • fallopian tubes
  • ureters
  • bowels and bladder
  • abdominal wall

In line with the menstrual cycle, the lesions grow and bleed, forming scar tissue. This bleeding, inflammation, and scarring cause the characteristic pain of endometriosis.

Diagnosis

A major issue with endometriosis is getting a diagnosis. 

A 2019 review in the American Journal of Obstetrics and Gynecology (AJOG) explained why this might be:

“Despite its high prevalence and cost, endometriosis remains underfunded and underresearched, greatly limiting our understanding of the disease and slowing much-needed innovation in diagnostic and treatment options.”

Researchers acknowledge that endometriosis presents complex diagnostic challenges. Because the symptoms vary so much, the condition is often misdiagnosed as bowel and digestive disorders. 

One 2020 United States study recorded that 75.2% of patients reported being misdiagnosed with another physical health (95.1%), a mental health problem (49.5%), or both before they received an endometriosis diagnosis. 

This study reported that misdiagnosis with a mental health problem was more common in those with younger age of endometriosis symptom onset.

The difficulty often leads to long delays between first reporting symptoms and a diagnosis of endometriosis. On average, women wait some 8.5 years for endometriosis to be confirmed, with some waiting much longer.

Doctors go through several stages to diagnose the condition, starting with palpating the abdomen to feel for lesions. They may use transvaginal ultrasound and MRI scans, but these do not always show lesions. 

Healthcare professionals can only make a firm diagnosis of endometriosis by laparoscopy. This is a surgical process done under general anesthesia where a camera is inserted through a small incision in the abdomen to view the pelvic organs.

Issues with diagnosis

A 2021 focus group study in the Netherlands identified several issues with diagnosing endometriosis:

  • Most women do not feel their symptoms are taken seriously.
  • Many women believe their experiences of menstruation are normal, often because of what they are told by their mothers, so they do not seek treatment.
  • Medical professionals find it hard to differentiate between “normal” menstrual complaints and signs or symptoms suggestive of endometriosis.

Treatments

Initially, most women are offered nonsteroidal anti-inflammatory drugs such as ibuprofen. However, little research has been done into whether these alleviate the severe pain caused by endometriosis, and anecdotal evidence suggests they have little effect.

As endometriosis is estrogen-dependent, medications that inhibit estrogen can be effective in controlling pain and inhibiting the growth of lesions. These include oral birth control pills and shots (Depo-Provera). However, some women experience side effects from these, such as headaches, irregular bleeding, and weight gain.

Gonadotropin-releasing hormone treatments offer an alternative. By suppressing reproductive hormones, they also restrict the growth of lesions. The side effect of suppressing these hormones is menopausal symptoms, such as hot flashes, tiredness, sleep issues, vaginal dryness, and joint pain. However, people can take low dose hormone replacement therapy to alleviate these.

For severe pain, or when other treatments have proven ineffective, surgery will be considered. Laparoscopy, as well as being used for diagnosis, is also used to remove endometrial lesions. 

Most people gain short-term pain relief after the removal of lesions, and for some, the effect is long lasting. However, according to the American College of Obstetricians and Gynaecologists, up to 80% of women see their pain return within 2 years.

As a last resort, hysterectomy — removal of the uterus — may be considered, but evidence for its benefits in treating endometriosis is inconclusive. It is a major irreversible procedure, and a woman who has a hysterectomy will no longer have periods or become pregnant.

Lack of research funding

In the U.S., endometriosis is diagnosed in approximately 1 in 10 women of reproductive age — diabetes is diagnosed in around 10% of the U.S. population, both male and female. 

In 2020, the U.S. government announced that funding for endometriosis research would be doubled to $26 million annually. In the same year, the National Institutes of Health (NIH) reported research spending on diabetes of $1,156 million.

Why the discrepancy? A 2021 study into gender disparity in research funding found that the “NIH applies a disproportionate share of its resources to diseases that affect primarily men, at the expense of those that affect primarily women.”

The authors went further, stating that diseases affecting primarily or solely men tended to be overfunded, whereas those affecting mostly or only women were underfunded.

And the pattern is repeated in the United Kingdom, where a 2018 analysis by the U.K. Clinical Research Collaboration found that only 2.1% of publicly funded medical research went to reproductive health and childbirth.

According to Emma Cox, Chief Executive of Endometriosis UK, the National Institute for Health Research has funded more than 8,000 projects since its inception in 2006, only 11 of which address endometriosis.

Taboo or ignorance?

“Women’s health, including endometriosis, has historically attracted far less research funding than other areas. We think this is because of a mixture of taboo and ignorance — whatever the reason, we are determined to put it right.”

– Emma Cox, Endometriosis UK

Lack of funding is not the only problem. Endometriosis is a complex condition. The symptoms vary so much between women that doctors used to think it was more than one condition. Therefore, it can be hard for researchers to know where to begin.

Some research has been done on animal models, but there are obstacles. Since primates are the most similar to people, they would be the best animals for modeling endometriosis. However, there are many objections to their use.

To avoid this problem, a team led by Prof. Philippa Saunders, chair of reproductive steroids at the University of Edinburgh, is developing a mouse model to study endometriosis. “The lowest species in which we can really do something meaningful is the mouse. That’s why the mouse is such an important model in reproductive research,” she says.

The researchers are studying the early development of the disease, with the aim of finding indicators of endometriosis in the blood. They hope this might provide a way of identifying the disease early before damage occurs.

However, Prof. Saunders is frustrated by the lack of funding for endometriosis research: “This progress was only possible because of increased pressure from patient groups who have been much more vocal over the last few years, working with clinical professionals to lobby funders.”

The way forward

According to the 2019 review of endometriosis research in AJOG, “[c]omprehensive and interdisciplinary approaches to disease management and increased education and disease awareness for patients, healthcare providers, and the public are needed to remove stigma, increase timely and accurate diagnosis and treatment, and allow for new advancements.”

Emma Cox is one of many calling for more action:

“We would like government and other funders to address the historic underfunding of endometriosis research in order to identify the cause of the condition, work towards a cure, and develop better treatments. Developing better treatments is vital given that endometriosis can be a chronic and debilitating condition and current treatment options don’t work for everyone.”

As recently as 2020, the UK’s All-Party Parliamentary Group (APPG) on Endometriosis report highlighted that the cause of the condition was still unclear.

“Historically, with limited investment in research into women’s health in general, there’s been so little investment in research into endometriosis that we don’t even know what causes it, and without knowing the cause, a cure cannot be found,” it says.

The APPG called for “[c]ommitment for vital investment in research into the cause of endometriosis, treatment and management options, and diagnosis,” adding that:

“Without investment in research, this condition will rob the next generation of women [of] the education, care, and support they deserve.”

Lobbying groups and charities in both the U.K. and U.S. are working hard to raise awareness of endometriosis. But what is really needed is government commitments to fund more research. 

Whether these will be forthcoming remains to be seen. 

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