Has your gynecologist ever measured the thickness of your uterine lining (endometrium) during an appointment? Studies show that having a thicker lining raises your risk of endometrial and uterine cancers. This is especially true for those who have already gone through menopause and no longer get their menstrual periods.

In this article, we’ll discuss how endometrial thickness relates to your cancer risk. We’ll also review the tests used to measure your endometrium and highlight key symptoms to watch for and discuss with your obstetrician/gynecologist (OB/GYN).

How the Endometrium Changes Over Time

The endometrium is the tissue that lines the inside of the uterus. As you go through your menstrual cycle (period), this lining thickens. During menstruation, this lining is shed. The thickness of the endometrium changes constantly throughout the menstrual cycle. The endometrium also grows thicker during pregnancy, to support the developing fetus.

In some cases, the endometrial lining can grow too much and become thicker than it should be. This is known as endometrial hyperplasia. There are several types of hyperplasia. If you have hyperplasia, doctors will want to test your endometrial cells under a microscope to see if they look normal, or typical. Having cells that look abnormal is called atypia.

If you have endometrial hyperplasia and your cells look normal, your risk of cancer is lower. If you have hyperplasia with atypia, it means you have abnormal-looking cells that are more likely to become cancerous. Atypical cells are more likely to develop into uterine or endometrial cancers.

Endometrial Thickness During Menopause

During menopause, the endometrium usually becomes thinner. But sometimes, it grows thicker instead. This can happen when your body makes too much estrogen — which thickens the tissue — and not enough progesterone. The drop in progesterone usually signals to the uterus to shed the endometrium during a menstrual period. Without enough progesterone, the lining stays thick.

When estrogen levels stay high while progesterone remains low, the endometrium may overgrow. Sometimes the lining’s cells clump together and become atypical. This condition, called endometrial hyperplasia, can become a risk factor for developing endometrial cancer over time.

Endometrium and the Risk of Endometrial Cancer

Studies show that endometrial thickness is linked to the risk of endometrial cancer. The thicker the uterine lining, the higher your chances of cancer. Researchers have found that people experiencing vaginal bleeding have a higher risk of cancer if their endometrium is thicker than 5 millimeters (mm). Those who don’t have any vaginal bleeding are at risk if their endometrium is thicker than 11 mm.

Endometrial thickening can be concerning, especially when it happens along with vaginal bleeding. Studies show that people who bleed vaginally after menopause have a 5 percent to 10 percent chance of developing endometrial cancer. For those without vaginal bleeding, thickened lining may still point to their cancer risk.

Endometrial hyperplasia can be treated to lower cancer risk. Without treatment, the risk of cancer is higher. About 8 percent of people with simple atypical hyperplasia develop cancer. For those with complex atypical hyperplasia, a more severe type, the risk rises to nearly 30 percent.

How Do Doctors Measure Endometrial Thickness?

Measuring endometrial thickness can be a normal part of your OB/GYN exam, especially after menopause. To do this, your doctor will likely use either an ultrasound or magnetic resonance imaging (MRI). The type of test used will depend on symptoms and health concerns.

During a transvaginal ultrasound, your doctor inserts a small, smooth wand in your vagina to look inside your uterus. The wand emits safe sound waves that bounce off your tissues, creating pictures of your organs. Transvaginal ultrasounds give doctors more detailed pictures of the uterus than abdominal ultrasounds (done on your stomach).

What’s the Average Endometrial Thickness?

The average thickness of the endometrium varies significantly from person to person, particularly depending on whether or not you’ve started menopause. It can also change depending on your hormonal cycles and menstruation.

In premenopausal individuals, the endometrium fluctuates throughout the menstrual cycle. It’s thinnest during menstruation (2 to 4 millimeters) and thickest during ovulation (7 to 16 millimeters).

Postmenopausal individuals are more likely to develop endometrial cancer if their endometrium is thicker. At this stage, for people who don’t bleed vaginally, 8 to 11 millimeters of endometrial tissue is considered within the normal limits. Studies show that there is a 7 percent risk of cancer if the endometrium is thicker than 11 mm.

If you’re experiencing vaginal bleeding after menopause, doctors hope to find a thickness of less than 5 millimeters. If the tissue is thicker, the risk of cancer rises to 7 percent. It’s important to note that these ranges might vary if you’re taking hormone replacement therapy (HRT) or the hormonal drug tamoxifen, which is used to treat breast cancer.

When To Talk to Your Doctor About Signs of Endometrial Cancer

Abnormal bleeding during or after your menstrual cycle is usually a sign of a problem. People with endometrial hyperplasia can experience:

• Heavy menstrual periods
• Abnormal bleeding between periods
• Short menstrual cycles that last less than 21 days (normal cycles are 28 days)
• No menstrual period at all
• Vaginal bleeding after entering menopause

Many of these symptoms overlap with those seen in menopause. People going through this change usually have irregular menstrual periods and abnormal bleeding. You’ve officially entered menopause when your last period was more than 12 months ago.

If you have any vaginal bleeding during menopause, talk to your doctor right away. This may be a sign of endometrial cancer or another health condition. Your doctor can run some additional tests to check your uterine lining. They’ll also be able to rule out other causes, such as endometrial hyperplasia.

Tests After Confirming Endometrial Thickness

If your doctor finds that your endometrial lining is thicker than it should be, they’ll run some additional tests. Many of these tests help diagnose endometrial hyperplasia and confirm or rule out cancer. Examples include:

• Hysteroscopy — A test using a thin tube with a light and camera that’s inserted into the vagina and cervix to look inside your uterus
• Endometrial biopsy — A small tissue sample is taken from the uterine lining and checked under a microscope for signs of cancer.
• Dilation and curettage (D&C) — A minor procedure where a tissue sample is scraped from the uterine lining and studied under a microscope

Talk With Others Who Understand

MyEndometrialCancerTeam is the social network for people with endometrial cancer and their loved ones. On MyEndometrialCancerTeam, members come together to ask questions, give advice, and share their stories with others who understand life with endometrial cancer.

Has your doctor checked the thickness of your endometrial lining? Have you had other tests to check for endometrial cancer? Share your experiences in the comments below, or start a conversation by posting on your Activities page.