Polycystic ovary syndrome (PCOS) is a common condition that affects your hormones.

Polycystic ovary syndrome (PCOS) is a common condition that affects your hormones. It causes irregular menstrual periods, excess hair growth, acne and infertility. Treatment for PCOS depends on if you wish to become pregnant. People with PCOS may be at higher risk for certain health conditions, like diabetes and high blood pressure.

What is polycystic ovarian syndrome? 
Polycystic ovary syndrome (PCOS) is a hormonal imbalance that occurs when your ovaries (the organ that produces and releases eggs) create excess hormones. If you have PCOS, your ovaries produce unusually high levels of hormones called androgens. This causes your reproductive hormones to become imbalanced. As a result, people with PCOS often have irregular menstrual cycles, missed periods and unpredictable ovulation. Small follicle cysts (fluid-filled sacs with immature eggs) may be visible on your ovaries on ultrasound due to lack of ovulation (anovulation). However, despite the name "polycystic," you don’t need to have cysts on your ovaries to have PCOS. The ovarian cysts aren’t dangerous or painful.

PCOS is one of the most common causes of infertility in women and people assigned female at birth (AFAB). It can also increase your risk of other health conditions. Your healthcare provider can treat PCOS based on your symptoms and if you wish to become pregnant.

What age does PCOS start? 
Women can get PCOS any time after puberty. Most people are diagnosed in their 20s or 30s when they’re trying to get pregnant. You may have a higher chance of getting PCOS if you have obesity or if other people in your biological family have PCOS.

How common is PCOS? 

PCOS is very common — up to 15% of women of reproductive age have PCOS.

What are the signs of polycystic ovary syndrome (PCOS)? 

The most common signs and symptoms of PCOS include:

Irregular periods 

Abnormal menstruation involves missing periods or not having a period at all. It may also involve heavy bleeding during periods.

Abnormal hair growth 

You may grow excess facial hair or experience heavy hair growth on your arms, chest and abdomen (hirsutism). This affects up to 70% of people with PCOS.

Acne 

PCOS can cause acne, especially on your back, chest and face. This acne may continue past your teenage years and may be difficult to treat.

Obesity 

Between 40% and 80% of people with PCOS have obesity and have trouble maintaining a weight that’s healthy for them.

Darkening of the skin 

You may get patches of dark skin, especially in the folds of your neck, armpits, groin (between the legs) and under your breasts. This is known as acanthosis nigricans.

Cysts 

Many people with PCOS have ovaries that appear larger or with many follicles (egg sac cysts) on ultrasound.

Thinning hair 

People with PCOS may lose patches of hair on their head or start to bald.

Infertility 

PCOS is the most common cause of infertility in people AFAB. Not ovulating regularly or frequently can result in not being able to conceive.

What is the main cause of PCOS? 
The exact cause of PCOS is unknown. There’s evidence that genetics play a role. Several other factors, most importantly obesity, also play a role in causing PCOS:

Higher levels of male hormones called androgens 

High androgen levels prevent your ovaries from releasing eggs, which causes irregular menstrual cycles. Irregular ovulation can also cause small, fluid-filled sacs to develop on your ovaries. High androgen also causes acne and excess hair growth in women and people AFAB.

Insulin resistance 

An increase in insulin levels causes your ovaries to make and release male hormones (androgens). Increased male hormones suppress ovulation and contribute to other symptoms of PCOS. Insulin helps your body process glucose (sugar) and use it for energy. Insulin resistance means your body doesn’t process insulin correctly, leading to high glucose levels in your blood. Not all individuals with insulin resistance have elevated glucose or diabetes, but insulin resistance can lead to diabetes. Having overweight or obesity can also contribute to insulin resistance. An elevated insulin level, even if your blood glucose is normal, can indicate insulin resistance.

Low-grade inflammation 

People with PCOS tend to have chronic low-grade inflammation. Your healthcare provider can perform blood tests that measure levels of C-reactive protein (CRP) and white blood cells, which can indicate the level of inflammation in your body.