Polycystic ovary syndrome (PCOS) is a condition in which women typically have a number of small cysts around the edge of their ovaries (polycystic ovaries). They also have one or more additional symptoms.
Symptoms of PCOS include irregular or light periods, problems getting pregnant, weight gain, acne and excessive hair growth.
Women with PCOS either fail to ovulate (see box), or they ovulate infrequently, which is why it is one of the leading causes of fertility problems.
Polycystic ovaries
Polycystic ovaries are ovaries containing a large number of harmless cysts that are no bigger than 8mm each. Normal ovaries have only about half this number of cysts.
The cysts are egg-containing follicles that have not developed properly (see box) because of a hormone imbalance (see Causes).
Often in PCOS, none of these follicles develops enough to release an egg, meaning ovulation does not take place.
Also, in some women, levels of the hormone testosterone (or other male hormones) are higher than normal, which results in many of the typical symptoms.
Many women have polycystic ovaries without having the syndrome (without the symptoms). Some women have the syndrome, but have normal looking ovaries on ultrasound.
How common is it?
PCOS affects millions of women in the UK.
About one in five women in the UK have polycystic ovaries, and approximately one in 10 have PCOS to some degree.
Who is affected?
Many women with PCOS are overweight or obese, and have an acquired form of PCOS. They may have excessive body hair and hair loss from the head.
PCOS also tends to run in families. If you have PCOS but are not overweight, you probably have a history of PCOS in your family.
Women with PCOS may also have a family history of diabetes and high cholesterol.
Outlook
PCOS cannot be cured, but the symptoms can be treated. Treatment options include lifestyle advice (losing weight) and the combined contraceptive pill.
If PCOS is not properly managed, it can lead to problems in later life, such as type 2 diabetes and high cholesterol levels.
Cyst
A cyst is a fluid-filled sac or cavity in the body.
Ovaries
Ovaries are the pair of reproductive organs that produce eggs and sex hormones in females.
Uterus
The uterus (also sometimes known as the womb) is a hollow, pear-shaped organ in a woman where a baby grows during pregnancy.
Swelling
Inflammation is the body's response to infection, irritation or injury. It causes redness, swelling, pain and sometimes a feeling of heat in the affected area.
Testosterone
Testosterone is a male sex hormone that is involved in making sperm. It causes the development of male sexual characteristics, such as the voice getting deeper. Testosterone is also found in small amounts in women.
Ultrasound
Ultrasound scans are a way of producing pictures of the inside of the body using sound waves.
