Understanding Endometriosis -- the Basics

Medically Reviewed by Traci C. Johnson, MD on September 15, 2023
4 min read

Endometriosis is a common condition in women. It's chronic, it's painful, and it often gets steadily worse.

Normally, the tissue that lines a woman's uterus, known as the endometrium, is found only in the uterus. But when a woman develops endometriosis, microscopic bits of this tissue grow on other organs such as the ovaries, the outer wall of the uterus, the fallopian tubes, the ligaments that support the uterus, the space between the uterus and the rectum, and the space between the uterus and the bladder. In rare cases, they can spread outside the abdomen and grow on other organs, such as the lungs.

Just like the endometrium, the tissue responds to the hormones estrogen and progesterone by thickening, and it may bleed intermittently. But because the tissue is growing in other tissues, the blood it makes cannot escape. This causes irritation to the surrounding tissue, which causes cysts, scars, and the fusing of body tissues. This can eventually bind the reproductive organs together and lead to infertility.

Cases of endometriosis are classified as minimal, mild, moderate, or severe, depending on the size of the lesions and how deeply they reach into the other organs. They are also referred to as stage I-IV.

Endometriosis affects 3% to 10% of women of reproductive age, and 25% to 50% of infertile women. It affects about 40% to 80% of women with pelvic pain. It affects all races equally. Symptoms usually get better after menopause.

Researchers don't know why or how endometrial tissue reaches other parts of the body. But there are some trends. Endometriosis tends to run in families. Endometriosis occurs more often in women who have short menstrual cycles or a longer-than-normal flow: Women who have fewer than 25 days between periods or who menstruate for more than 7 days are twice as likely to develop endometriosis. And dioxin, an industrial chemical, may be a cause.

How the disease causes infertility also is unclear. Some researchers think endometriosis tissue upsets the process of ovulation. The tissue may also block eggs from moving through the fallopian tubes. Others think that the tissue makes chemicals that interfere with fertilization. But more study is needed to provide answers.

Myth: Endometriosis is just a really heavy period.

During your monthly cycle, hormones cause the lining of your uterus to thicken to get ready for a possible pregnancy. If you don’t get pregnant, you get your period. The tissue breaks down and exits through your vagina.

Endometriosis happens when those hormones trigger thickening and bleeding in the tissue growing outside your uterus, like on your ovaries or in the tubes that deliver your eggs (the fallopian tubes). This often makes you bleed more during your period, but not always.

Myth: Heavy bleeding means you have endometriosis.

Not necessarily. It’s one possible cause, but other things could be to blame, like:

  • Growths such as polyps and fibroids
  • Thyroid problems
  • Pregnancy
  • Cancer

Myth: Serious pain is normal during your period.

Talk to your doctor if pain interferes with your daily routine. It’s a common sign of endometriosis and of other problems. And the pain may not be limited to your period. Endometriosis can also cause pain between periods, when you go to the bathroom, or during sex.

Myth: You can’t get it when you’re young.

If you’ve started your period, you can get endometriosis. It’s more likely once you get into your 30s and 40s, but your chances also go up if:

  • Other family members have had it
  • You start your period young

It typically takes 7 to 10 years to diagnose. Talk to your doctor if you notice symptoms like pain, heavy bleeding, bad cramps, bloating, and spotting between periods.

Myth: It’s all in your head.

Endometriosis is a physical condition, not a mental one. Blood and tissue buildup can lead to bloating, inflammation, scar tissue, and pain. But years of long, painful periods and uncomfortable sex can take its toll on your mental health, especially if you don’t know what causes them. That’s why it’s important to see a doctor, usually a gynecologist. In a large city, you might find a doctor who specializes in endometriosis. They can help you diagnose and manage your condition.

Myth: Your symptoms signal how serious it is.

Not always. You could have advanced endometriosis with no obvious symptoms, or a mild case that causes intense pain and other issues. Pain probably comes from the scarring and irritation caused by bleeding, or from endometrial tissue growing on a nerve.

Myth: Something you did caused your endometriosis.

Doctors don’t know what causes endometriosis, though it runs in families. Also, the hormone estrogen seems to make the condition worse. Things like douching or having an abortion don’t cause it.

Myth: Endometriosis means you can’t get pregnant.

Not necessarily. Most women with the condition are able to have children. But the more serious the disease, the more likely you are to have problems. Your doctor may be able to help with certain treatments if you have trouble getting pregnant because of endometriosis.

Myth: Pregnancy cures endometriosis.

There’s no cure for endometriosis. Your doctor can use hormones, pain meds, and, in serious cases, surgery, to manage the condition. During pregnancy, you don’t have your period. Levels of the hormone progesterone rise, which often eases endometriosis symptoms. But they’ll probably return after you give ­­­birth or after you finish breastfeeding.