EC Basics

The exact cause of endometrial cancer (EC) is not known, but it is associated with several risk factors.

These include hormonal imbalances, hormonal therapy for breast cancer, the number of periods in a lifetime, lack of pregnancy, age, race and genetics.

Hormonal imbalance

An imbalance between the two female hormones, estrogen and progesterone, can increase the risk of EC.

This imbalance can be caused by diabetes, obesity and irregular ovulation patterns, as in the case of polycystic ovary syndrome.

Hormone replacement therapy with just estrogen and no progesterone can also cause EC. In fact, there was a sharp increase in the number of EC cases in the 1960s when estrogen replacement therapy was widely prescribed. The number of cases started to decline when this practice was given up.

An ovarian tumor that produces high levels of estrogen can also lead to hormonal imbalance and increase the risk of EC.

Hormonal therapy for breast cancer

A drug called Tamoxifen, which is used to prevent breast cancer, has been associated with an increased risk of EC. However, the risk is very low, at around 1%, and the benefits of the treatment usually outweigh its risks.

Number of periods in a lifetime

The number of periods a woman has in her lifetime is associated with the risk of developing EC, with a higher number of periods increasing the risk of EC. 

In other words, starting periods at a younger age and reaching menopause at an older age may increase the risk of EC. 

This is thought to be caused by the fact that the lining of the uterus is exposed to estrogen for longer.

Lack of pregnancy

Never having been pregnant also increases the risk of developing EC. In other words, a woman who has never been pregnant is at an increased risk of EC compared to a woman who has been pregnant at least once. More pregnancies decrease the risk of EC even further.

This is because the levels of progesterone are high during pregnancy, which is protective against EC. 

Breastfeeding is also associated with a reduced risk of EC.

Age

The risk of EC increases with age, and the disease mainly affects women after menopause. The average age of having EC is 60, and the disease is uncommon among women who are below the age of 45.

Race

Research has shown that Black women have a higher risk of being diagnosed with advanced EC compared to white women. Post-menopausal Black women are at particularly high risk of EC. 

Black and Hispanic people are also at a higher risk of developing more aggressive tumors.

Genetics

Genetic factors may also be associated with the risk of EC. For example, a genetic condition known as Lynch syndrome is associated with an increased risk of EC as well as other types of cancer, including colon cancer.

Another genetic condition that increases the risk of EC is Cowden disease, also known as multiple hamartoma syndrome, which is a rare genetic disease characterized by the presence of benign or non-cancerous growths in different parts of the body.