by Emily Poulin
figures by Brad Wierbowski

“Have you heard of endometriosis?”

As a scientist and a woman, I was embarrassed to say that I hadn’t. Although I had seen two doctors about my pelvic pain, it was a friend who first mentioned endometriosis to me.

My reaction turns out to be pretty common. Although endometriosis affects about ten percent of women, many have never heard of it, including those who suffer from it.

I have always had painful periods, but doctors had always prescribed me oral contraceptives or higher doses of painkillers and sent me on my way.

Not one had mentioned endometriosis.

What is endometriosis?

Figure 1: The female reproductive system. The female reproductive system is centered on the uterus, where a fertilized egg implants and develops into a fetus. Eggs develop in the ovaries and, once every month, one is released into the fallopian tubes for travel to the uterus. At the base of the uterus is the cervix, which leads out of the uterus, releasing any unfertilized eggs and menstrual fluid.

Endometriosis is a disorder of the endometrium, which is the inner lining of the uterus. Every month, the endometrium thickens in preparation for implantation of a fertilized egg (Figure 1). In the absence of implantation, the endometrium breaks down and is shed during menstruation. Endometriosis occurs when endometrial tissue finds its way outside the uterus, but how this happens remains unknown. The most common hypothesis is retrograde menstruation, or the reverse flow of menstrual fluid; instead of exiting the uterus through the cervix, the fluid flows backwards out of the fallopian tubes and into the abdomen (Figure 2). Endometrial tissue in this fluid can attach to the outside of pelvic organs like the uterus, bladder, or intestines. Once attached, this rogue endometrial tissue continues with business as usual: every month, it can thicken in anticipation of an embryo and shed when one isn’t present. In this scenario, however, blood from the endometrial attachments enters the body cavity and causes severe pain.

Figure 2: Retrograde menstruation is the prevailing hypothesis for endometriosis development. The endometrium (uterine lining) grows and thickens every month in preparation for implantation of a fertilized egg. In one’s absence, the endometrium sheds during menstruation. Normally, menstrual fluid exits the uterus through the cervix (middle, top) and is expelled from the body. However, when retrograde menstruation occurs (middle, bottom), menstrual fluid exits the fallopian tubes near the ovaries and empties into the body cavity. This is one possibility for how endometrial tissue, carried in retrograde menstrual fluid, reaches the pelvic cavity. This endometrial tissue can attach to pelvic organs, resulting in endometriosis, the main symptom of which is pain (dark red rings).

How is endometriosis diagnosed and treated?

A definitive endometriosis diagnosis is difficult to make using non-invasive procedures. Since the main symptom is pelvic or abdominal pain, endometriosis is often mistaken for other conditions that present with similar symptoms, such as inflammatory bowel disease.

Figure 3: Treatment options for endometriosis do not include a cure. The most non-invasive treatment commonly used to treat endometriosis is continuous use of an oral contraceptive or intrauterine device (IUD) (left), which reduces pain (light red rings) and menstrual fluid, slowing endometriosis progression. Laparoscopic surgery (middle) is a minimally invasive surgery used to definitively diagnose endometriosis and remove endometrial attachments on pelvic organs. Laparoscopy can relieve endometriosis pain, but does not prevent recurrence. Hysterectomy (right) is the surgical removal of the uterus, which reduces endometriosis-related pain and the major source of the disease, the endometrium. Although the endometrium is removed in this process, endometriosis recurrence does occur in some patients who have had a hysterectomy.

Suspected cases may be treated with continuous oral contraceptive use or a hormone-releasing intrauterine device (IUD) like Mirena (Figure 3, left). These interventions help alleviate pain and decrease menstrual flow, thereby reducing the chances of endometrial tissue traveling outside the uterus. However, women experience varying degrees of responsiveness and side effects to these options, so although they may be effective in some, they are far from a comprehensive solution.

A conclusive endometriosis diagnosis is made by surgical intervention, usually a procedure called a laparoscopy (Figure 3, middle), during which a small camera is inserted through a small incision in the abdomen. This allows a surgeon to visualize the rogue endometrial tissue and remove it by burning it off or excising it. Although this procedure can relieve pain temporarily, it does not treat the underlying cause of the disease.

Aside from living with what can be extreme pain, 30-50% of women with endometriosis experience infertility. Women may need multiple surgeries to continually remove and manage their endometriosis if they want to have children. If the disease progresses too far, some may be forced to resort to a hysterectomy (surgical removal of the uterus), which eliminates the source of the problem, the endometrium (Figure 3, right). Unfortunately, in addition to the risks that accompany any major surgery, a hysterectomy is not a cure, and endometriosis recurrence can still occur.

Because endometriosis is so difficult to diagnose, it is not uncommon for women to wait years for a definitive diagnosis to be made. During this time, women with endometriosis suffer from pain, and they may become infertile if the disease progresses. This delay can cause immense frustration among women who, had they known, may have tried to have children sooner elected to have a hysterectomy, or taken additional proactive measures to mitigate disease symptoms. In addition, they may incur significant individual health care costs due to tests, surgeries, and expensive fertility treatments.

What are clinicians and researchers doing to address endometriosis?

Choosing between pain and surgical management or surgical sterilization is not a reasonable choice. So what is being done to study endometriosis and improve the options?

Women are often told their period pain is normal. While certain discomforts are associated with that time of the month, pain that disrupts normal life is not normal. Having to stay in bed for a day due to period pain is not normal. Missing work or class because of pain is not normal. Understanding that disruptive menstrual pain is not normal is the first step, and women who experience it should see a doctor and consider the possibility of endometriosis.

Unfortunately, unlike conditions like strep throat, endometriosis cannot be diagnosed by a routine, one-size-fits-all test—it is a varied disease that we still do not fully understand. The main symptom of endometriosis is pain, but it is extremely difficult to quantitatively measure a patient’s pain, and it is even more difficult to compare pain between different patients.

To bring researchers and doctors together to combat these challenges, Dr. Linda Griffith co-founded the MIT Center for Gynepathology Research (CGR) in 2009. The CGR “brings together over 15 laboratories and clinical practices in the Boston area and around the world to foster both basic and clinical research in endometriosis, infertility, pre-term birth, sexually-transmitted disease, and other pathologies of the female reproductive tract.”

I spoke with Dr. Griffith, who described the efforts of researchers and clinicians at the CGR who are developing ways to better categorize patients and quantify pain. “Our hypothesis is that there are multiple different subsets of patients and they probably need different care,” Griffith said.

Figure 4: New research approaches to endometriosis. The Griffith lab at MIT is using systems biology to stratify patients based on molecular signatures and identify targeted treatments based on patient categories (different patient colors, right). Clinicians at Newton-Wellesley Hospital are measuring patient activity with the goal of quantitatively measuring endometriosis-related pain (dark and light red rings, bottom) and developing potential pain-based treatments.

Unlike certain cancers, where defined genetic changes inform treatment, population- level genetic changes in endometriosis are not well defined. Therefore, Griffith’s lab uses systems biology, a computational modeling approach to study molecular changes at a comprehensive level, in patients with endometriosis. They hope to categorize patients based on these changes, which may lead to treatment insights (Figure 4).

In addition, doctors at Newton-Wellesley Hospital are studying whether a wireless device called Emerald, which measures patient activity, might be able to quantify pain. Emerald uses wireless signals to track a person’s movements. The device is installed in the home and measures activity, even through walls, without the patient needing to wear a device.

Using Emerald, the researchers hope to determine whether a patient’s activity levels correlate with their pain. If such a relationship exists, then Emerald’s measurements of activity could be translated into an objective, quantifiable measure of pain. According to Dr. Griffith, the goal is to obtain “more objective data to understand the patient experience, then develop a set of standards for more general practice…and a set of criteria to determine whether they should be operated on.” These innovative ways to understand endometriosis and improve diagnostic methods have great promise for women struggling with the disease, hopefully leading to more meaningful treatment options.

Emily Poulin is a postdoctoral fellow at Beth Israel Deaconess Medical School and Harvard Medical School.

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