Overview of PCOS

Polycystic ovary syndrome (PCOS), also called Stein-Leventhal syndrome, is a condition that occurs in women. PCOS is characterized by high levels of certain male hormones (called androgens). The condition, which causes irregular menstrual periods and other symptoms, is the most common cause for infertility in women.

The ovaries are the female reproductive glands. They are located in the pelvis, one on each side of the uterus (womb). Ovaries produce and store female reproductive cells (eggs, ova) and secrete hormones (estrogen, progesterone) that are responsible for secondary sex characteristics, such as breast development and body hair.

Eggs are stored in fluid within tiny follicles (cysts or sacs) in the ovaries. Normally, in women of childbearing age, a number of eggs begin to develop about every 28 days. Usually, one of the eggs matures fully and fluid builds up within the cyst until the follicle breaks open, releasing the mature egg (ovum). This process is called ovulation.

The ovum then moves into the fallopian tube, where it can be fertilized by a male reproductive cell (sperm). Whether or not the egg is fertilized, it continues through the fallopian tube to the uterus. A fertilized egg implants in the uterus and results in pregnancy. If the egg is not fertilized, menstruation occurs.

In women who have PCOS, ovulation does not occur regularly. The ovaries do not produce enough progesterone, none of the eggs is released, and the fluid-filled cysts remain in the ovary. Polycystic ovaries produce high levels of androgens, which interfere with ovulation further and cause symptoms of PCOS.

In January 2013, an independent panel of the U.S. National Institutes of Health (NIH) recommended changing the name of this disorder to one that more accurately defines the condition. More information is to follow.

Incidence and Prevalence of PCOS

According to the U.S. Department of Health & Human Services, polycystic ovary syndrome affects approximately one in ten women of childbearing age. The condition can occur in girls as young as 11 years old. Overall incidence is higher in women who are Native American and Hispanic than in Caucasian and African American women.

PCOS Causes and Risk Factors

The cause for PCOS is unknown. Research has shown that a number of factors may contribute to development of the condition. Polycystic ovary syndrome may have a genetic (inherited) risk factor; however, no gene has been identified. Women whose mother or sister has PCOS are at increased risk for developing the condition.

High insulin levels can increase production of androgens (e.g., androsterone, testosterone) and contribute to PCOS. Insulin is a hormone secreted by the pancreas that is necessary to convert glucose (sugar) into a form that can be used by cells for growth and energy. In some women who have PCOS, the body does not use insulin normally, leading to abnormally high levels of the hormone and increasing androgen production.

Although androgens are "male hormones" and are responsible for the development of male characteristics (e.g., facial hair, deep voice), women also produce lower levels of these hormones in the ovaries, fat cells, and the adrenal gland. In women, high levels of androgens interfere with ovulation and cause other symptoms associated with PCOS (e.g., weight gain, increased hair growth, acne).

Publication Review By: Stanley J. Swierzewski, III, M.D.

Published: 29 Oct 2007

Last Modified: 01 Oct 2015