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If you're a woman with polycystic ovary syndrome (PCOS for short), some of your hormones will be out of balance. These hormones affect your menstrual cycle (your periods), your weight and the way hair grows on your body.

You might find having polycystic ovary syndrome upsetting. It can make it harder to have children. Some symptoms, like unwanted body hair, can be embarrassing. But you're not alone. Lots of women have this condition. And there are some good treatments that can help.

PCOS is sometimes called polycystic ovary disease.

• Polycystic ovary syndrome means you have problems with your hormones, particularly the ones that are made in your ovaries.
• You may have irregular periods, or even none at all. You may also get unwanted hair on your face and body, put on weight, and have oily or spotty skin.
• Having PCOS can mean problems getting pregnant for some women. But lots of women with PCOS are able to have children, either with or without treatment.
• Losing weight may help with some of the symptoms of PCOS.
• There are also several drugs that can help women with PCOS.

Hormones are chemicals your body makes. They control all sorts of things that happen in your body. The hormones that are affected by PCOS help to control:

• Your periods
• Getting pregnant
• The way your hair grows on your face, head and body
• Your skin
• Your weight.

Several hormones are made in your ovaries. Your ovaries are two small organs in your abdomen. They are part of your reproductive system. They're connected to your uterus by tubes called fallopian tubes. The hormones that your ovaries make are called estrogens, androgens and progesterone. The amount of hormones your ovaries make is affected by other hormones, which are made by a gland near your brain.

As well as making hormones, your ovaries release eggs. Usually, your ovaries release one egg a month. This is called ovulation.

If you're healthy, the levels of hormones in your body go up and down as you go through your menstrual cycle. When your hormones are at a certain level, your ovaries release an egg. The egg travels towards your uterus. If you have sex around this time, sperm can fertilize the egg. The egg then attaches itself to the wall of your uterus and grows into a baby. But if you don't get pregnant, the thick lining of the wall of your uterus breaks down, and you have a period.

The hormones in your body all affect one another. For example, insulin is a hormone that controls how much sugar (glucose) you have in your bloodstream. But the amount of insulin in your blood also has an effect on the amount of androgens your body produces.¹ Androgen hormones affect your sex drive, your skin, the way your hair grows and how much energy you have.

If you have polycystic ovary syndrome, some of the hormones in your body are out of balance.¹ Usually, the hormones that affect your period go up and down through your menstrual cycle. If you have PCOS, they may stay at the same level instead.²

This means that the parts of your body that are controlled by these hormones may not work the way they should. Your ovaries may not release eggs regularly. So you don't get regular periods. This can make it hard for you to get pregnant.

As well as affecting your periods, hormones affect lots of other things your body does. Androgen hormones can change fine hairs on your body into longer, thicker hair, like the hair that grows on your head, in your armpits or in your bikini area. Women with PCOS sometimes have slightly raised levels of androgens. This can cause thicker hair in unwanted places.

Androgens can also make the pores in your skin produce more oil. This can give you pimples (acne).³

PCOS also seems to affect the way your body responds to a hormone called insulin. Insulin affects the amount of sugar in your blood and the way your body uses energy. Having a lot of insulin can also make you produce more androgens.

Doctors think that your hormones are likely to have been out of balance right from when you first started to get your periods. But you might not notice it for a few years, because young girls often have irregular periods at first.¹

Women with PCOS often have small fluid-filled swellings (cysts) on their ovaries. That's how polycystic ovary syndrome gets its name. Polycystic means with lots of cysts. Doctors don't know exactly why some women get these cysts.

Often, putting on weight can make the symptoms of PCOS more noticeable. Doctors don't think that having PCOS makes you overweight, but women with PCOS often find it very hard to lose weight.¹

We don't know why some women get polycystic ovary syndrome. But it seems to run in families. So, the genes you inherit from your parents may play a part.⁴

• About 4 in 10 women with PCOS have a sister with it.
• About 2 in 10 women with PCOS have a mother who had it.

This information is for educational use only, and is not a substitute for prompt professional medical advice. Readers should always consult a physician or other professional for advice and treatment. ©BMJ Publishing Group Limited 2008. All rights reserved.