Polycystic ovary syndrome (PCOS)

PCOS causes irregular menstrual periods because monthly ovulation does not happen and levels of androgens (male hormones) are high. This happens in 5 to 10 out of 100 of women.

The high androgen levels can lead to:

  • Extra facial hair growth
  • Acne
  • Male-pattern scalp hair thinning
  • Being overweight or obese
  • Being at higher risk of having diabetes and obstructive sleep apnea

People with PCOS can get pregnant, but it may be harder. They often need fertility pills or shots to help them ovulate.

PCOS is life long, but can be treated to lessen symptoms. Most people with PCOS lead a normal life without many complications.

Causes of PCOS

The cause of PCOS is not totally understood. It is believed abnormal levels of the luteinizing hormone (LH) and high levels of male hormones (androgens) interfere with normal function of the ovaries.

What happens in a normal menstrual cycle

In a normal menstrual cycle, the brain, pituitary gland, ovaries, and uterus follow a sequence of events each month. This gets the body ready for pregnancy. Two hormones, follicle-stimulating hormone (FSH) and LH, are made by the pituitary gland. Two other hormones, progesterone and estrogen, are made by the ovaries.

  1. During the first half of the cycle, FSH rises to cause the ovary to make a follicle with an egg (oocyte). The follicle raises the level of estrogen. This causes the lining of the uterus to thicken and the pituitary to release a very large amount of LH.
  2. The midcycle surge of LH causes the egg to be released from the ovary (ovulation). If the egg is fertilized by a sperm, it turns into an embryo and travels through the fallopian tube to the uterus.
  3. After ovulation, the ovary makes estrogen and progesterone to get the uterus ready for possible embryo implantation and pregnancy.

What happens in a menstrual cycle in PCOS

During a menstrual cycle in PCOS many small follicles (small cysts) form in the ovary, hence the term polycystic ovaries. None of these small cysts can grow to a size that would trigger ovulation. As a result, the levels of estrogen, progesterone, LH, and FSH become imbalanced.

Androgens, such as testosterone, androstenedione, dehydroepiandrosterone (DHEA), and DHEA sulfate (DHEAS), are often made by the ovaries and the adrenal glands. Androgens may be higher in people with PCOS because of the high levels of LH, and also because of high levels of insulin often seen with PCOS.

Metabolic system abnormalities

The metabolic system controls the processing of carbohydrates, fats, and proteins. Hormones in the metabolic system are insulin, glucagon, glucagon-like peptides, and many others.

High levels of insulin are often found in the blood of people with PCOS.

Insulin is a hormone made by special cells in the pancreas. Insulin regulates blood glucose levels. When blood glucose levels rise, such as after eating, these cells make insulin to help the body use glucose for energy.

  • If glucose levels do not respond to normal levels of insulin, the pancreas makes more insulin. This is called hyperinsulinemia.
  • When high levels of insulin are needed for normal glucose levels, a person is said to be insulin resistant.
  • When the blood glucose levels are not controlled, even with higher amounts of insulin, the person is said to have glucose intolerance. This is sometimes called prediabetes.
  • If blood glucose levels keep rising even with higher insulin levels, the person is said to have type 2 diabetes.

Insulin resistance and hyperinsulinemia can happen in both normal-weight and overweight people with PCOS. Up to 35 out of 100 people with PCOS and obesity have prediabetes by age 40. Up to 10 out of 100 people with PCOS and are obese have type 2 diabetes.

You are at higher risk for these if you:

  • Have PCOS when compared with women without PCOS
  • Have family history of diabetes
  • Are overweight or obese
  • Are African American and Hispanic

Signs of PCOS

The changes in hormone levels described in the previous section can cause:

  • Absent or irregular menstrual periods
  • Body hair growth
  • Scalp hair loss
  • Acne
  • Difficulty getting pregnant

Signs of PCOS often start about the time of puberty. Some people do not have signs until early adulthood though. People can have mild to severe signs because hormonal changes differ from one person to the next.

Weight gain and obesity

1/2 of all people with PCOS often have a slow weight gain and obesity. For some people, this starts at the time of puberty.

Hair growth and acne

Male-pattern hair growth (hirsutism) may be seen on the upper lip, chin, neck, sideburns, chest, upper or lower abdomen, upper arm, and inner thigh. Acne causes oily skin and blockages in hair follicles.


Many people with PCOS do not ovulate regularly. This can lead to getting pregnant taking longer. An infertility evaluation is often needed after 6 to 12 months of trying to become pregnant.

Heart disease

Women who are obese and also have insulin resistance or diabetes might be at higher risk of coronary artery disease. This can lead to a heart attack. It is not known for sure if women with PCOS are at higher risk. Both weight loss and treatment of insulin abnormalities can lower the risk. Other treatments, such as cholesterol-lowering medicines and treatments for high blood pressure may also be offered.

Sleep apnea

This causes brief spells where breathing stops (apnea) during sleep. People with this problem often feel very tired during the day. Also, people with sleep apnea that is not treated have a higher risk of insulin resistance, obesity, diabetes, and cardiovascular problems, such as high blood pressure, heart attack, abnormal heart rhythms, or stroke. Up to 50 out of 100 women with PCOS may have sleep apnea. It is diagnosed with a sleep study. There are many ways to treat it.

Other problems

Women with PCOS also have a higher risk of:

  • Depression and anxiety
    • These can be treated with therapy and medicines.
  • Sexual dysfunction
    • People with PCOS are more likely to have lower sexual satisfaction.
  • Eating disorders, such as:
    • Bulimia
    • Binge eating

PCOS diagnosis

There is not a test to diagnose PCOS. People are diagnosed based on symptoms, blood tests, and an exam.

Experts found people with PCOS must have 2 out of 3 of the following:

  • Irregular menstrual periods caused by no or irregular ovulation.
  • High androgen levels that cause extra hair growth, acne, male-pattern balding, or high levels in blood tests.
  • Polycystic ovaries on pelvic ultrasound.

You can learn more about PCOS using these resources:

Last reviewed: 
January 2021

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