Skip Navigation

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:


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

Other signs include:

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:

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:

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:

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.


Additional Resources

Home Health Testing Guides

Testing Company Reviews

Related Topics

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.