Endometrial cancer is the form of uterine cancer that’s most commonly diagnosed. Women can be at higher risk for endometrial cancer for several reasons, including health conditions and lifestyle factors that can boost their estrogen levels. Polycystic ovarian syndrome, or PCOS, is one of those health conditions known to increase a woman’s chances of developing endometrial cancer.

Ovaries produce the hormone estrogen and the egg that is released monthly — a process called ovulation — during a woman’s reproductive years. PCOS is a condition of the female reproductive system that causes a bunch of small cysts, which are tiny sacs of fluid, to form on the ovaries. Women with PCOS typically don’t ovulate and have abnormally high levels of androgen hormones, often called “male” hormones.

Women with PCOS also have increased levels of estrogen and abnormally low levels of progesterone, another hormone.

The Estrogen Factor

Hormone levels play a big role when it comes to cancer risk — particularly types of uterine cancer like endometrial cancer. Women with PCOS and other factors that increase estrogen levels — including obesity, diabetes, or taking medications like tamoxifen (Nolvadex, Tamosin, Tamofen, Tamoxen) or estrogen replacement therapy — are more likely to develop endometrial cancer than those without these factors. The abnormal amounts of estrogen are particularly risky when not balanced by sufficient progesterone levels in the blood. This is why post-menopausal women who have not had a hysterectomy and who need treatment for severe menopausal symptoms will be prescribed both estrogen and progesterone, instead of estrogen alone.

Estrogen therapy

Treating the symptoms of menopause with hormones is known as menopausal hormone therapy (or sometimes hormone replacement therapy). Estrogen is the major part of this treatment. Estrogen treatment can reduce hot flashes, improve vaginal dryness, and help prevent the weakening of the bones (osteoporosis) that can occur with menopause.

Doctors have found, however, that using estrogen alone (without progesterone) can lead to type I endometrial cancer in women who still have a uterus. To lower that risk , a progestin (progesterone or a drug like it) must be given along with estrogen. This approach is called combination hormone therapy.

Women who take progesterone along with estrogen to treat menopausal symptoms do not have an increased risk of endometrial cancer. Still, taking this combination increases a woman’s chance of developing breast cancer and also increases the risk of serious blood clots.

If you are taking (or plan to take) hormones after menopause, it is important to discuss the possible risks (including cancer, blood clots, heart attacks, and stroke) with your doctor.

Like any other medicine, hormones should be used only at the lowest dose that is needed and for the shortest possible time to control symptoms. As with any other medicine you take for a long time, you’ll need to see your doctor regularly. Experts recommend yearly follow-up pelvic exams. If you have any abnormal bleeding or discharge from the vagina you should see your doctor or other health care provider right away (and not wait for a check-up).

For more information about the cancer risks from taking hormones after menopause, see Menopausal Hormone Therapy and Cancer Risk.

Progesterone is the hormone responsible for the monthly “shedding” process of the endometrium — or the lining of the uterus. This process results in monthly menstruation, which many women with PCOS don’t have because of insufficient progesterone levels. Without progesterone and monthly periods, the endometrium becomes thick and the cells may become altered, leading to a precancerous condition called endometrial hyperplasia. Eventually, endometrial cancer may develop if PCOS is left untreated.

Reducing Your Endometrial Cancer Risk

While you can’t prevent PCOS, it’s important to know your risk for endometrial cancer and figure out what you can do to protect your health and minimize that risk.

If you have PCOS, do what you can to keep other risk factors for endometrial cancer in check:

  • Treat your PCOS. If left untreated, hormone levels will remain abnormal and affect your whole body and your cancer risk. Seek treatment for PCOS early and regulate hormone levels. You can do this with oral contraceptives — progesterone-only pills are best to reduce endometrial cancer risk — or metformin (Glucophage, Glucophage XR, Glumetza, Fortamet, Riomet), the diabetes medication, to manage hormone production. Surgery may also be an option.
  • Reach and maintain a healthy body weight. Most often, women with PCOS are obese or overweight. And obesity is a known risk factor for endometrial cancer because it also increases estrogen levels. By getting regular exercise and sticking to a healthy diet, you can lose excess pounds and minimize your endometrial cancer risk, even if you have PCOS.
  • Avoid fat in your diet. Besides helping avoid unwanted pounds, trimming the fat from your diet can reduce endometrial cancer risk. It’s thought that fat affects the way that estrogen is metabolized and used by the body, which can also raise the chances of developing endometrial cancer.
  • Get regular Pap smears and pelvic exams. If you already know you’re at a greater risk for endometrial cancer because of your PCOS, it’s important to keep an eye out for early signs of cancer. Having a regular pelvic exam done by your gynecologist can help to identify endometrial cancer and begin treatment.

Having PCOS doesn’t mean you’re destined to develop endometrial cancer, but it does mean that you’re at an increased risk for the disease. So take good care of yourself by focusing on preventive care, maintaining a fit body, and living a healthy lifestyle to reduce your endometrial cancer risk.