The Most Common Ovarian Cyst Causes, According to Ob-Gyns

These noncancerous growths are usually harmless, but sometimes they can become severe and warrant medical attention.

For the most part, the vagina gets the majority of the attention when it comes to female reproductive organs—and while it does serve as the birth canal (and primary sex organ), it's only one part of an entire reproductive system made of many different organs and body parts.

One of those organs‚—which technically comes as a pair—are the body's ovaries, or the small, oval-shaped glands located on either side of the uterus, attached to the fallopian tubes. The body's ovaries produce eggs and hormones, and they play an important role body's menstrual cycle each month, and are the starting point for possible conception.

But, as helpful as the ovaries are, they can also develop ovarian cysts, or noncancerous growths that can form inside or on the surface of the ovary. Though most cysts don't cause any discomfort and often go away on their own, larger cysts can cause abdominal pressure, bloating, swelling, and pain in the lower abdomen, on the side of the ovary with the cyst, according to the Office on Women's Health. More severe symptoms can include sharp pain with nausea and vomiting, which is a sign that you need emergency medical attention, usually consisting of surgical removal.

There are a few different causes of ovarian cysts (and, because of that, different types of ovarian cysts)—here's what you need to know about each one.

Your menstrual cycle

Functional cysts—aka, follicular cysts and corpus luteum cysts—form at different parts of the menstrual cycle and usually go away on their own. The follicle is a clear sac of fluid containing the egg as it prepares to be released during ovulation. “There are times where you could have a follicle that grows and grows and grows, and doesn’t necessarily release an egg, and that’s what we would call a follicular cyst,” Dr. Rebecca Brightman, assistant clinical professor of Obstetrics, Gynecology, and Reproductive Science at Mount Sinai, tells Health. “Typically, they can come, they go, they can cause some discomfort at times, rarely does someone need surgery for something like that.”

After releasing the egg in ovulation, the follicle closes back up and starts producing estrogen and progesterone to prepare for pregnancy. When fluid also accumulates, the corpus luteum (a mass of cells that form in the body to start producing progesterone) becomes a corpus luteum cyst. “Sometimes the post-ovulatory cyst, which we call the corpus luteum cyst, can also become quite large, and can rupture or burst, which can cause pain,” Dr. Brightman says. Usually, the pain resolves itself on its own, the cyst goes away after two or three menstrual cycles. “But there are times when people need surgical intervention, although that’s rather rare.”


Not all people with endometriosis suffer from cyst growth. “Endometriosis is the presence of little implants, or lesions that are similar to the uterine lining, outside the uterus. That doesn’t necessarily mean there’s going to be a cyst,” Dr. Brightman says. Those implants are called uterine endometrial cells, and sometimes, when they grow outside the uterus, they attach to ovaries and can form endometriomas.

Endometriomas are also referred to as “chocolate cysts,” Dr. Mary Rosser, Assistant Professor of Obstetrics & Gynecology at Columbia University, tells Health. That's because an endometrioma contains old blood and tissue. “That’s why it causes so much pain during a period, when you’re sloughing off your uterine lining, then it also causes bleeding from this uterine lining-type tissue that’s in the cyst,” she explains. “So it’s old blood, tissue, like you get from your uterine lining, and because the old blood is usually dark, that’s how it’s got its name of ‘chocolate cyst.’” Usually, these are painful, but some women don’t have symptoms, and discover them on ultrasounds.


It’s normal for a corpus luteum cyst to form after fertilization, Dr. Brightman says, and it becomes important during pregnancy. That cyst will produce the hormone progesterone and support the embryo through the first trimester, after which the placenta can start making progesterone itself. For people who get pregnant through in vitro fertilization (IVF), “they take a supplemental progesterone because they don’t have that cyst,” she says.

“There may be a cyst seen on the ovary when we’re diagnosing a pregnancy on ultrasound,” Dr. Rosser says. Again, these corpus luteum cysts are producing estrogen and progesterone throughout the first several weeks of pregnancy, until the placenta can effectively function on its own, after which point, the cyst resolves itself. Most women don’t experience pain or bleeding from the cyst, and many don’t realize it’s there at all. However, Dr. Rosser says, “if a patient has pain or bleeding, we ask them to come in for evaluation.”

A congenital condition

Dermoid cysts are less common, and are a congenital condition, meaning they develop in the womb, so a woman with one of these cysts has likely had it her entire life. “It develops from ovarian tissue and the eggs,” Dr. Rosser says, because these embryonic cells become trapped during fetal development. “It can contain tissues that are not actually from the ovary, like fat cells, hair, teeth, skin, and bone. It’s very interesting-looking, if you remove it in the operating room.” Ovarian dermoid cysts are usually diagnosed once a woman reaches reproductive age (especially around age 30), because they can cause pain during the menstrual cycle. They’re not often cancerous, but surgery may be indicated to remove them.

“Honestly, with ultrasound, if they’re small, we frequently leave them alone,” Dr. Brightman says. “If they get to be larger than about six centimeters or so, or if a woman is symptomatic, then we remove them, typically via laparoscopy.” Though balls of hair, teeth and bone might sound scary, dermoid cysts are fairly common, and represent 1 in 5 abnormal growths on the ovaries, beyond functional cysts.

Polycystic ovary syndrome (PCOS)

Polycystic ovary syndrome is exactly what it sounds like—many cysts on the ovary. “They’re tiny little follicular cysts that never go past a very early stage, and they are usually situated on the periphery of the ovary, and they look like a ‘strand of pearls’ on ultrasounds,” Dr. Rosser says.

PCOS affects between 5% and 10% of women between the ages of 15 and 44, and many women discover it when they have trouble getting pregnant as a result of irregular menstrual cycles, per the Office on Women’s Health. Women with PCOS are more likely to have diabetes, high blood pressure, sleep apnea, and depression/anxiety, but researchers don’t know whether PCOS causes these issues or vice versa, or whether there’s another underlying condition at play causing all of the above.

STDs and pelvic infections

Since 2017, gonorrhea, chlamydia, and syphilis have been on the rise. Those infections can cause pelvic abscesses, which are sacs filled with pus. “Due to this infection, a patient will not feel well and usually has pelvic pain and fever,”Dr. Rosser says. “That is why it is important for us to regularly screen for STIs and encourage women to engage in safe sexual practices.”

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