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An illustration of a uterus, fallopian tubes and ovaries. The left ovary has many different different shapes of eggs, and right ovary has none.

Illustration by Marta Pucci

Reading time: 9 min

Polycystic Ovary Syndrome (PCOS) 101

Top things to know:

  • Polycystic Ovary Syndrome (PCOS) is a common disorder, but it remains undiagnosed and unmanaged in most people who have it

  • Some of the most common symptoms include irregular periods, hair growth on the face and body, acne, infertility, and weight gain

  • PCOS is manageable when diagnosed, and lifestyle changes have been shown to make a big difference. Management is important in preventing any long term health risks.

  • It’s still not understood what causes PCOS. It is characterized by insulin resistance and inflammation, and may involve a mix of genetic and environmental factors.

What is PCOS?

Polycystic Ovary Syndrome (PCOS) is a condition in which certain hormones are out of balance. These imbalances typically show up as irregular menstrual cycles, a higher level of androgens (a type of hormone including testosterone) in the body, and small cysts in the ovaries. PCOS can cause symptoms including excess facial and body hair, acne, and mood changes. It can also make it difficult to become pregnant, and may significantly harm a person’s overall health if left untreated.


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About 8 in 10 people who have PCOS have irregular cycles (1). About 7 in 10 people with PCOS have high testosterone (1). High testosterone causes symptoms including facial and body hair (hirsutism), hair loss on the head, and acne. Not everyone with PCOS develops small cysts in their ovaries—cysts are a symptom of PCOS, rather than a cause. While they can contribute to hormonal imbalances, the cysts themselves are usually harmless (2). PCOS cysts are different than the kind of ovarian cysts that grow, rupture, and cause pain.

PCOS is very common. It may affect roughly 1 in 12 women and people with cycles of reproductive age (8%, or ~6-13%), but this likely varies across populations (3-7). Of those who have it, about 7 in 10 may go undiagnosed (7,8). Unmanaged PCOS can impact short and long term health. It’s associated with type 2 diabetes, infertility, cardiovascular disease, obesity, sleep apnea (disrupted breathing in sleep), non-alcoholic fatty liver disease, and depression (9-11). Early diagnosis and treatment can help reduce these risks significantly. Healthcare providers can often give a diagnosis after a short assessment or simple tests.

PCOS symptoms: what you might notice

PCOS can look and feel different for everyone. Some of the most common PCOS symptoms are:

PCOS symptoms may start around the same time as a person’s first period (menarche). This can lead people to think their cycles or symptoms are normal when they might not be. If symptoms appear around the same time as a first period, or if periods are consistently irregular (infrequent, absent) 2–3 years after menarche, it’s a good idea to talk to a healthcare provider.

Symptoms of PCOS may become more noticeable with time, or only become apparent after someone gains a lot of weight (14).

Why it happens: causes of PCOS

PCOS is a complex disorder of the endocrine system. This system is a network of hormone-producing glands which regulate reproductive and sexual function, sleep, stress, and more. But it’s still not exactly clear what causes PCOS, and it probably varies for different people. Genetics, behavior, lifestyle, and environment may all play a role.


PCOS can likely be passed down genetically in families (15-17). That means someone is much more likely to have the disorder if a first-degree relative also has it. One study found that people with PCOS have mothers with the disorder about one-fourth of the time, and a sister with the disorder one-third of the time (18). Another study found that identical twins were about twice as likely as non-identical twins or sisters to both have PCOS (19). It’s still unclear which genes are involved in PCOS-risk inheritance. Researchers are looking into hereditary differences in a person’s production of and sensitivity to certain hormones, such as those involved in the brain-ovary connection (like GnRH, FSH, or LH), or androgen hormones, or insulin. There may be hereditary differences in the process of how ovaries prepare eggs for release leading up to ovulation. Another theory is that PCOS susceptibility stems from differences in how weight and energy are regulated in some people (15-17).


For some people with PCOS, hormonal imbalances are likely caused by insulin excess (12, 20). Insulin, the hormone important for processing sugar/glucose, also acts as a signal to the ovaries to produce testosterone. When someone is insulin resistant—when they have a lower sensitivity to insulin for processing glucose—their body adjusts by making more insulin. This leads to higher levels of testosterone, which can slow or stop the growth and release of eggs from the ovary, and suppress the production of hormones like estrogen and progesterone that go along with a functioning menstrual cycle (20, 21). About a half to two-thirds of people with PCOS have been found to be insulin resistant—a group which may also tend to experience more symptoms and health complications of the disorder over time (20, 22).


Inflammation is when tissue becomes red, swollen, and warmer than usual, often in response to an injury or infection. You can see inflammation at work when you cut yourself or twist an ankle. But inflammation inside the body can also happen in response to illness, obesity, stress, and even genetics. As with insulin resistance, inflammation causes the body to produce extra insulin, creating the same pathway to testosterone production. People with PCOS are much more likely to have chronic low-grade inflammation, which is measured via blood tests for C-reactive protein (CRP—a marker of inflammation in the body) (23-25). The root cause of inflammation in people with PCOS is still unclear.


Researchers, including Clue’s collaborator and PCOS researcher Dr. Shruthi Mahalingaiah are looking into the role of environmental endocrine-disrupting chemicals (EDCs) in causing PCOS. Prenatal or developmental exposure to certain compounds in consumer products, air pollution, and cigarettes may predispose a baby to develop PCOS later in life (26). Some of the compounds being investigated are nicotine, bisphenol A (BPA), phthalates, and triclocarban. They can be found amongst plastics, cosmetics, soaps, clothing, toys, carpets, school supplies, pacifiers, and in air pollution. These compounds may alter the fetal environment by changing the levels of androgens and estrogens, and may contribute to PCOS-related changes in fetal programming, particularly for those with genetic predispositions to the disorder (26-28).

Why get it checked out

PCOS is underdiagnosed and undertreated. This may be because symptoms can be mild or seem unrelated. But untreated PCOS can lead to a wide range of more serious health conditions, and the symptoms of the disorder can cause significant distress. Affiliated risks include type 2 diabetes, infertility, sleep apnea (disrupted breathing in sleep), non-alcoholic fatty liver disease, cardiovascular disease, depression, or even uterine cancer (9-11). In all cases, it’s important to have PCOS diagnosed as early as possible, and managed with the help of a healthcare provider.

How PCOS is diagnosed

PCOS is usually diagnosed when someone meets at least two of the following three criteria:

  • Irregular cycles, especially ones that are long or absent

  • Evidence of androgen excess (hyperandrogenemia) such as excess body hair or hair thinning on the scalp and/or high levels of androgenic hormones (like testosterone) in the blood

  • Having a number of cyst-like sacs in the ovaries (3,6)

A healthcare provider will probably ask questions about your symptoms and your medical and menstrual history and perform a simple physical exam. If they think PCOS may be present, they may also:

  • Ask questions about your full health history, including medical and surgical history, social history, and family history

  • Perform blood tests to check the levels of hormones and sugars in the blood. Hormones they will typically check for include: testosterone, thyroid hormone, prolactin, and tests of sugar metabolism.

  • Perform a pelvic ultrasound (sonogram) of your ovaries and uterus

Infrequent or absent menstrual periods can be caused by other health conditions, such as having a thyroid disorder (an over- or underactive thyroid gland). When doing a blood test, your healthcare provider may include an assessment of thyroid hormone levels, as well as levels of the hormone prolactin (which is high in people with hyperprolactinemia—another cause of infrequent or absent periods). This may be especially important for people who have no other obvious symptoms related to PCOS. Issues with prolactin or thyroid hormones can also overlap in some people, and one condition can contribute another, which is why tests may be important in getting a diagnosis.

PCOS treatment and management: what you can do about it

PCOS is a lifelong condition, but there are many options to help minimize symptoms and prevent complications in the future. How PCOS is treated will depend on the potential cause of the PCOS, and each person’s symptoms and goals. These are just some of the options:

Lifestyle changes

Diet, exercise, and behavioral changes can have a big impact in preventing and managing PCOS (29). Reestablishing regular ovulation will help with the symptoms and health impacts of the condition. For some people with a lot of non-essential body fat, weight loss of more than 5% (with dietary changes) may help in restoring ovulatory function, and improving symptoms like facial hair growth (32). Limiting simple carbohydrates and sugars in the diet can help keep insulin in balance, and may prevent inflammation, but there isn’t yet strong evidence that one diet is best for everyone (30–34). Weight loss can be more difficult for people with PCOS, and weight can be easier to put on, so self-compassion is important. Symptoms of anxiety and depression may also be improved with lifestyle changes (29).


Birth control pills are often prescribed as a first-line treatment after or with lifestyle changes. Antidiabetic medication and anti-androgen medication are sometimes prescribed to help balance hormones. Metformin is a drug sometimes prescribed to help regulate blood sugar in some forms of PCOS. People who are trying to get pregnant might be prescribed a drug to help them ovulate (15-17). Antidiabetic medications, which can improve the way the body uses insulin, are sometimes prescribed in combination with other measures to help manage weight (17, 24). Some people seek out complementary medicine including herbal treatments and supplements to help with PCOS symptoms. More research needs to be done on the effectiveness of these approaches for PCOS.

Tracking your PCOS symptoms

Tracking your cycle and the symptoms you experience can help in advocating for yourself with a healthcare provider. Here are some suggested symptoms you can track in Clue.

Essential to track:

  • Bleeding patterns

Helpful to track:

  • Skin (if you have acne)—some people with PCOS develop acne that changes with their cycle

  • Weight (or diet tracking)

  • Digestion

  • Stool

  • Pain

  • Moods

  • Any other symptoms you might be concerned about

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