It's estimated that one in 10 women experience endometriosis during their reproductive years, a condition where cells that line the uterus go rogue by moving to other organs, taking root and spreading there, leading to terrible pain. Many women who have the disorder struggle to be properly diagnosed.

As Linda Griffith, a top biological engineer at MIT, relates in a recent New York Times article by Rachel Gross, it was years before she knew why she was experiencing exceptionally heavy periods and debilitating pain.

"I was told it was normal. I was told that I was under stress ... [that] I was rejecting my femininity," Griffith says now.

When a doctor finally diagnosed her with endometriosis in the late 1980s, Griffith says, "I was relieved to know that finally somebody found something wrong with me — because I knew something was wrong."

Her treatment involved hormone therapy and multiple surgeries, including a hysterectomy. Her personal experience, Griffith says, has informed her research, as she's come to see the study of the endometrium as a great way to unlock some of the mysteries of tissue regeneration.

Griffith first became famous in the science world for her work in grafting living tissue shaped like a human ear onto the back of a mouse — an achievement that's helping tissue engineers figure out the rich mix of factors needed to grow skin and cartilage for human transplant. In 2009, she co-founded the MIT Center for Gynepathology Research, where she broadened the scope of her work to include endometriosis.

"The regeneration of the endometrium is weirdly not studied as much as it should be," she says. "But it's fascinating because you get about a centimeter of growth of tissue that has beautifully formed blood vessels, an immune system, all of the structures of the tissue — over a period of about two weeks."

To understand endometriosis and find better treatments, she says, society needs to become more comfortable addressing women's reproductive health in general.

"It is not acceptable in society really to talk about your period," she says. "There's many period problems: Heavy menstrual bleeding, fibroids, all of these kinds of things. You just don't talk about your period. So that has to change."

Interview highlights

On the remarkable qualities of the cells of the endometrium, which is shed each month when a women gets her period and which then regenerates

There's very rapid cell growth. There's no scarring in a normal individual, and understanding that might help us with heart regeneration and other kinds of wound healing. ... There's also an enormous influx of different kinds of immune cells throughout the cycle we don't really understand: Are immune cells migrating in from blood? Are they proliferating in place? We know that certain kinds of immune cells in the uterus are very different than elsewhere in the body. So there's a lot of fascinating things that orchestrate this beautiful event every month going on under the direction of these hormones.

On what is happening in the body with endometriosis

We don't know exactly what causes it, but what we find in patients is that the lining of the uterus, the endometrium, is found growing outside the uterus. It can grow on the lining of the abdomen. It can invade the bladder, it can invade the bowel. It can land on the ovaries and cause a big cyst. When it causes symptoms and it's found growing there, we call it endometriosis.

On why endometriosis can be so painful

We don't know all of the reasons. There's a lot of speculation around why it causes so much pain. It could be because there's inflammation that comes from leaking blood every time the woman has her period. The little lesions that are growing in the abdomen also can bleed. They cause the blood vessels to become very leaky. And whenever you have an accumulation of blood, you get inflammation. This can send signals for pain.

Think about it: When you even just get a paper cut, it hurts, right? Now imagine that you have a whole bunch of those all over the inside of your body. It's going to hurt for the same reasons and more. If you have something like a blister that goes on and you're continually irritating it, it's going to hurt. Later, when the disease progresses, you can get distortion of the internal organs. The ovary may spin out of place. This can pull on a nerve all the time. So it's like you're constantly, constantly being kicked or something, because that nerve is being pulled all the time by the distortion of the organs that comes from scar tissue that builds up and glues things together.

On the notion of "period privilege," and how it can prevent women from being diagnosed with endometriosis

Some women just don't understand that other women could have these terrible, terrible things happening, because they themselves don't experience those symptoms. "Period privilege," as I'm calling it, could be active or passive. Passive is just they don't think about it and they kind of find it hard to believe. But active — and I encountered this a lot — is women saying, "It can't be that bad." And some of these women are gynecologists, like the one who treated my niece who had endometriosis, and the gynecologist told my sister my niece was making everything up. So I think period privilege is one of those things where women who don't have menstrual problems don't believe the women who do. Either just they don't think about it, or they actively say, "Don't talk about it," because it makes women look weak.

On the prevailing theories about how endometrial tissue migrates

There's potentially a lot of different ways it could happen. There are theories that during [fetal] development you have migration of cells from the neural crest and you get cells migrating all over the body to their respective ultimate positions. And sometimes [with] the cells moving along in a train, some cells fall off the train. And then when you go through puberty, the cells that fell off the train are sitting there and they can develop into the endometrium or other tissues. So that is a probable cause in some women — that they had a developmental issue.

There's also a lot of evidence that in ... people who are in their 20s or 30s, that menstrual tissue, instead of all going out the cervix as it should, it goes out the fallopian tubes. And this happens in all women. When you have women undergoing surgery during their periods, you can find menses in the abdominal cavity. So it happens in all women. But what we don't know is why in some women it may not be cleared away by the immune system as it should. There are about 10% of women who have endometriosis. So why that tissue wouldn't be cleared away, we don't exactly know. Is it something strange about their endometrium? Is their endometrium very aggressive or is it something strange about their abdominal cavity? Is the immune system weak or not proper or is it fertile ground for the endometrium?

On why she initially hid her disease from her colleagues

I was diagnosed in 1988 and joined the faculty in 1991. ... That was at a time when the premier endocrinology textbook — I had to teach endocrinology at Harvard Medical School at the time — it had a tiny chapter, two or three pages, on endometriosis and it said: "The typical patient is a nulliparous [never given birth] white woman in her late 30s who's highly educated and has an anxious personality." The textbook said that. [In] 1991.

We call that a diagnosis bias. Because the people who would get diagnosed were the people who had resources and who would be persistent and had access to care.

We know endometriosis affects all different races, all different [societies] around the world — everybody has about the same incidence of endometriosis. So to get back to why didn't I study it? I just didn't want to think about it. At that time, you didn't talk about gynecology. You still don't talk about it if you have a gynecology disease and you're an engineering professor or any kind of science professor. So I hid. I had elaborate rituals — how I ran my life — to hide the fact that I had a gynecology disease. Nobody really knew it. You just didn't talk about it.

Amy Salit and Kayla Lattimore produced and edited the audio of this interview. Bridget Bentz, Molly Seavy-Nesper and Deborah Franklin adapted it for the Web.

Copyright 2021 Fresh Air. To see more, visit Fresh Air.

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