Abhishek Mahajan (narrator / author)

Heading.

Why is endometriosis interesting?

But before we get to my points, what actually is the clinical definition of endometriosis?

Plainly put, it is when tissue that resembles the uterine lining or endometrial-like tissue grows outside the uterus.

The tissue can implant itself in nearby tissues, like the ovaries and fallopian tubes, or even more distal organs like the bladder and bowel.

Due to the continuous influx of hormonal growth factors, mainly estrogen, these misplaced endometrial-like cells respond cyclically, just as the normal uterine lining does.

They thicken, break down, and bleed with each menstrual cycle, but unlike the uterine lining, they have nowhere to go.

Instead of exiting through menstruation, this trapped tissue and blood accumulates, causing severe pain, inflammation, fibrosis, scar formation, and adhesion between organs.

Over time, these repeated cycles of inflammation and fibrosis may lead to permanent structural changes within the abdomen and pelvis, contributing to chronic pelvic pain and infertility.

To segue into the first interesting aspect of the disease, how did the tissue get there in the first place?

What caused it to be trapped?

Well, it's a curious question, because... Subheading The primary hypothesis of why it exists is not complete.

Retrograde menstruation is perhaps the most culturally dominant theory as to why endometriosis occurs at all, first proposed by gynecologist John Sampson nearly 100 years ago.

The theory is straightforward.

During menstruation, some sloughed-off endometrial cells flow backward through the fallopian tubes into the pelvic cavity instead of outward through the cervix.

Once there, these cells implant themselves, continue growing, and become the endometrial-like tissue characteristic of endometriosis.

It's a clean and simple idea, one that is repeated by gynecologists constantly.

I don't have a great mental model for what this looks like, so I found the following picture helpful.

There's an image here.

If you look this theory up on endometriosis forums, most patients generally consider it to be unilaterally false.