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Polycystic Ovary Syndrome (PCOS)

Last Updated: Mar 1, 2019


Polycystic ovary syndrome, or PCOS, is a common type of hormonal imbalance that causes a variety of health problems in women. The condition is named for the multiple cysts (fluid-filled sacs) that form on the ovaries of most patients. PCOS is one of the leading causes of infertility among American women and is associated with menstrual difficulties, chronic health conditions and unwanted changes in appearance.

A healthy ovary and Fallopian tube

Under normal circumstances, human eggs develop in female reproductive organs called the ovaries. The ovaries also produce the sex hormones estrogen, progesterone and androgen, which regulate the menstrual cycle and reproductive process.

During a normal menstrual cycle, an egg grows in a fluid-filled pocket on the ovary surface called a follicle. When the egg matures, the follicle ruptures and releases it into the fallopian tube connected to the uterus. This process is known as ovulation.

In women with PCOS, ovulation is irregular or suppressed altogether due to a hormonal imbalance. In these cases, growing egg may not mature fully or erupt from the follicle. Without ovulation, the woman does not menstruate (have a monthly period), and the ovary does not produce the female sex hormone progesterone. The partially formed follicles may develop into fluid filled cysts on the ovary surface.

In addition to decreased fertility and irregular periods, the hormonal imbalances of PCOS can cause other problems. About 70 percent of patients experience hormonal symptoms such as male pattern baldness or excess hair growth on the face and body (hirsutism). About 80 percent of women with PCOS are obese. Having PCOS also elevates a woman’s risk of cardiovascular disease.

PCOS is quite common, affecting 5 to 10 percent of women of childbearing age (or about 5 million in the United States). Girls who begin puberty before age eight may be at increased risk for developing PCOS later on. While menstrual symptoms disappear at menopause, appearance issues and chronic illness risk usually persist across the life span.

Causes and Risk Factors

The direct cause of PCOS is a hormonal imbalance - specifically, an excess of hormones called androgens. These hormones are more plentiful in men’s bodies than in women’s and are responsible for secondary sex characteristics like facial hair, fat distribution and pattern baldness.

It’s unknown why some women seem to produce more androgens than others, but experts believe the following interrelated factors may play a role:

  • Genetics. PCOS appears to run in families.
  • Insulin resistance. Insulin is a hormone produced by the pancreas that helps the body’s cells convert blood sugar (glucose) into energy. When the body has trouble using insulin, the pancreas secretes more of it into the blood. It is theorized that excess insulin stimulates androgen production.
  • Low-grade inflammation. Immune response caused by food intolerances is linked to insulin resistance and cardiovascular disease. Studies show that women with PCOS are prone to this type of inflammation.
  • Exposure to excess androgens during fetal development. Some studies suggest that fetal androgen exposure may promote the development of abdominal fat in women, a pattern that is linked to both insulin resistance and low-grade inflammation.


A diagnosis of PCOS requires the presence of symptoms in at least two of the following clusters:

  • Menstrual problems. These can include excessively heavy or light periods, infrequent periods, a long menstrual cycle (35 days or more) or periods that stop for four months or longer.
  • High androgen levels. These can be measured directly by a blood test. Symptoms like thinning hair, pattern baldness, hirsutism (excess face and body hair) and adult acne can also indicate excess androgen.
  • Multiple small ovarian cysts. These develop in most (but not all) women with PCOS.

Other signs include:

  • Difficulty getting pregnant (female infertility)
  • Dandruff
  • Obesity or weight gain (especially around the waist area)
  • Thick, discolored skin patches
  • Skin tags
  • Pain in the pelvic area (may resemble menstrual cramping)
  • Anxiety or depression
  • Sleep apnea.

Diagnosis and Treatment

At present, no specific test exists that can diagnose PCOS. When a woman presents with PCOS symptoms, her doctor may use the following assessments to make a diagnosis:

  • Medical history and physical exam to check for irregular periods, weight issues, hair growth and other symptoms.
  • Pelvic exam to check the reproductive organs by sight and touch.
  • Blood tests to measure sugar, cholesterol and androgen levels.
  • Vaginal ultrasound, a test that uses reflected sound waves to create pictures of the pelvic organs.
  • Tests as needed to rule out other conditions.

To date, there is no cure for PCOS. Treatment focuses on managing each woman’s symptoms according to her needs and preferences and may include:

  • Birth control pills (combination or progesterone type) to help to restore normal hormone balance and relieve some symptoms.
  • Anti-androgen medications to help relieve appearance-related symptoms like hair loss and hirsutism.
  • Metformin (Glucophage®), a drug used to treat diabetes that has been shown to stimulate ovulation in some women.
  • Fertility drugs to stimulate ovulation in women who wish to become pregnant.
  • Weight loss and healthy diet to reduce insulin resistance, which in turn helps to restore healthy hormone balance and ovulation.
  • Ovarian drilling surgery. In this procedure, the surgeon passes a laparoscope (a tube with a camera in the end) through a small incision in the abdomen and uses an electric needle or laser to burn holes in the follicles on the ovaries’ surfaces. In some women, this lowers androgen levels, allowing more regular ovulation for the next few months.

Because PCOS can lead to serious complications, it’s important to start treatment as soon as possible. Having untreated PCOS increases a woman’s risk of:

  • Diabetes (more than half of women with PCOS develop type 2 diabetes or prediabetes by age 40)
  • Heart attack
  • High blood pressure
  • High cholesterol
  • Sleep apnea (a breathing problem during sleep)
  • Endometrial cancer
  • Nonalcoholic steatohepatitis (inflammation of the liver caused by accumulation of fats)
  • Anxiety and depression
  • Miscarriage
  • Pregnancy complications

Women with PCOS can reduce their risk of complications by maintaining a healthy weight and getting tested regularly for diabetes.


It’s unclear whether PCOS is preventable. In some cases, the condition appears to develop in response to substantial weight gain. Healthy diet and regular activity can help to keep weight stable and decrease insulin resistance.


  • “Polycystic ovary syndrome.” Larissa Hirsch. The Nemours Foundation, 2014. Accessed April 28, 2014.
  • “Polycystic ovary syndrome.” The American College of Obstetricians and Gynecologists, 2011. Accessed April 28, 2014.
  • “Polycystic ovary syndrome (PCOS).” Mayo Foundation for Medical Education and Research, 2011. Accessed April 28, 2014.
  • “Polycystic ovary syndrome (PCOS) fact sheet.” Ester Eisenberg. United States Office of Women’s Health, Department of Health and Human Services, 2012. Accessed April 28, 2014.

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Tina Shahian, PhD

Tina is a writer for Innerbody Research, where she has written a large body of informative guides about health conditions.


A communication specialist in life science and biotech subjects, Tina’s successful career is rooted in her ability to convey complex scientific topics to diverse audiences. Tina earned her PhD in Biochemistry from the University of California, San Francisco and her BS degree in Cell Biology from U.C. Davis. Tina Shahian’s Linkedin profile.


In her spare time, Tina enjoys drawing science-related cartoons.