Causes and Risk Factors of Polycystic Ovary Syndrome

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While researchers are not certain of the exact cause of polycystic ovary syndrome (PCOS), it is known that an imbalance of the endocrine system is responsible for many of the changes associated with it. A woman's ovaries and adrenal glands produce more androgens than normal, resulting in increased body hair, acne, and irregular periods. A combination of genetic, health, and lifestyle factors may play a role in these changes.

Common Causes

PCOS affects between 6% and 10% of women worldwide. Here is a look at the primary theories about why PCOS occurs.

The Hypothalamic-Pituitary-Ovarian Axis

Hormones are proteins produced by a structure in the body that causes a change within a cell or organ. Gonadotropin-releasing hormone (GnRH) is produced when the hypothalamus (a gland in the brain) is stimulated. GnRH travels to the pituitary gland, another small structure in the brain, which then produces a variety of other hormones that regulate and maintain many bodily functions.

Of significance to PCOS, the pituitary produces follicle stimulating hormone (FSH) and luteinizing hormone (LH). LH travels to the ovary where it stimulates the production of androgens.

The hypothalamic-pituitary-ovarian (HPO) axis is used to describe this system of hormonal control.

It has been hypothesized that persistently high levels of LH and androgens, namely testosterone, causes PCOS. However, this does not explain why many women with PCOS do not have high levels of LH.

The Insulin-Androgen Connection

Insulin has been thought to have a role in the development of PCOS. In addition to regulating glucose levels, insulin causes the liver to decrease production of a key molecule known as sex-hormone binding globulin (SHBG).

Testosterone is carried in the blood by SHBG when the molecule is present. If a reduced amount of SHBG is available, more free testosterone (that which is not carried by SHBG) is in the blood. It is also believed that high levels of insulin can increase the number of androgens that the ovary produces.

This also does not fully explain PCOS, as many women with the condition do not have insulin resistance (a change in how cells react to insulin), although it is a common issue seen in PCOS.


One key aspect of PCOS is that it runs in families. Women with PCOS often have a sister, mother, cousin, or aunt who also has the condition. While other possible causes are debatable, PCOS clearly has a link to heredity.​

Every day researchers become closer to identifying the genetic abnormalities that may be to blame. This is difficult due to the lack of a single diagnostic test as well as the role that other factors (such as diet and exercise habits) may play in the development of the disease.

Common variations in the genes that control the production of androgens, luteinizing hormone, anti-Mullerian hormone, energy production, insulin production, insulin regulation, inflammatory response, and fat production may be responsible.

20% to 40% of women with PCOS have a mother or sister who has PCOS.

Lifestyle Risk Factors

PCOS is more often seen in women who are obese. It isn't clear whether being overweight causes PCOS or is a result of having PCOS. Keep in mind that many women who have normal weight also have PCOS.

According to the Centers for Disease Control and Prevention (CDC), lifestyle factors that lead to insulin resistance may raise your risk of PCOS. These include being sedentary and eating an unhealthy diet. Losing weight will often improve the symptoms of insulin resistance.

A Word From Verywell

It can be frustrating to have a condition that has no clearly identifiable cause. But if you have PCOS or type 2 diabetes in your family, you can work on modifying your risk factors. Even with PCOS, you can reduce your risks of complications by striving to maintain or reach a normal weight. At any weight, being active with exercise and reducing your sedentary time will improve your risks and may help control the symptoms associated with insulin resistance.

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