The exact cause of polycystic ovary syndrome (PCOS) is unknown, but it’s thought to be related to abnormal hormone levels.

Resistance to insulin

Insulin is a hormone produced by the pancreas to control the amount of sugar in the blood. It helps  move glucose from blood into cells, where it is broken down to produce energy.

Insulin resistance means the body’s tissues are resistant to the effects of insulin. The body therefore has to produce extra insulin to compensate.

High levels of insulin cause the ovaries to produce too much testosterone hormone, which interferes with the development of the follicles (the sacs in the ovaries where eggs develop) and prevents normal ovulation.

Insulin resistance can also lead to weight gain, which can make PCOS symptoms worse because having excess fat causes the body to produce even more insulin.

Hormone imbalance

Many women with PCOS are found to have an imbalance in certain hormones, including:

• raised levels of testosterone – a hormone often thought of as a male hormone, although all women normally produce small amounts of it
• raised levels of luteinising hormone (LH) – a hormone that stimulates ovulation, but may have an abnormal effect on the ovaries if levels are too high
• low levels of sex hormone binding globulin (SHBG) – a hormone that helps reduce the effect of testosterone
• raised levels of prolactin (only in some women with PCOS) – a hormone that stimulates the breast glands to produce milk in pregnancy

The exact reason why these hormonal changes occur is not known. It’s been suggested that the problem may start in the ovary itself, in other glands that produce these hormones, or part of the brain that controls their production. The changes may also be caused by the resistance to insulin.

Genetics

Polycystic ovary syndrome (PCOS) sometimes runs in families. If any relatives, such as your mother, sister or aunt, have PCOS then the risk of you developing it is often increased.

This suggests there may be a genetic link to PCOS, although specific genes associated with the condition have not yet been identified.

See your GP if you have any typical symptoms of polycystic ovary syndrome (PCOS).

Your GP will ask about your symptoms to try and rule out other causes and check your blood pressure.

Your GP or specialist may then request an ultrasound scan, which can show if you have a high number of cysts in your ovaries (polycystic ovaries). The cysts are under-developed sacs in which eggs develop, called follicles. 

You may also need a blood test to measure your hormone levels and to screen for diabetes or a high cholesterol level.

Diagnosis criteria

A diagnosis of PCOS can usually be made if other rare causes of the same symptoms have been ruled out and you meet at least two of the following three criteria:

• you have irregular or infrequent periods – this indicates your ovaries do not regularly release eggs (ovulate) 
• blood tests show you have high levels of “male hormones” (androgens), such as testosterone (or sometimes just the signs of excess male hormones even if the blood test is normal)
• scans show you have polycystic ovaries

As only two of these need to be present to diagnose PCOS, you will not necessarily have to have an ultrasound scan and blood test before the condition can be confirmed.

Referral to a specialist

If you are diagnosed with PCOS, you may be treated by your GP or referred to a specialist – either a gynaecologist (specialist in treating conditions of the female reproductive system) or an endocrinologist (specialist in treating hormone problems).

Your GP or specialist will discuss with you the best way to manage your symptoms. They will recommend lifestyle changes, and start you on any necessary medication.

Follow-up

Depending on factors like your age and weight, you may be offered annual checks of your blood pressure and screening for diabetes if you’re diagnosed with PCOS.

Polycystic ovary syndrome (PCOS) is a common condition that affects how a woman’s ovaries work.

PCOS affects millions of women in the UK.

The three main features of the condition are:

• cysts that develop in your ovaries (polycystic ovaries)
• your ovaries do not regularly release eggs (ovulate)
• having high levels of “male hormones” called androgens in your body

You will usually be diagnosed with PCOS if you have at least two of these features.

Read more about diagnosing polycystic ovary syndrome.

What are polycystic ovaries?

Polycystic ovaries contain a large number of harmless cysts up to 8mm in size. The cysts are under-developed sacs in which eggs develop. Often in PCOS, these sacs are unable to release an egg, meaning ovulation doesn’t take place.

It’s estimated that about 1 in every 5 women in the UK has polycystic ovaries, but more than half of these have no symptoms.

Signs and symptoms

Symptoms of PCOS usually become apparent during your late teens or early twenties. They can include:

• irregular periods or no periods at all
• difficulty getting pregnant (because of irregular ovulation or failure to ovulate)
• excessive hair growth (hirsutism) – usually on the face, chest, back or buttocks
• weight gain
• thinning hair and hair loss from the head
• oily skin or acne  

Polycystic ovary syndrome is associated with an increased risk of problems in later life, such as type 2 diabetes and high cholesterol levels.

You should speak to your GP if you think you may have PCOS.

Read more about the symptoms of polycystic ovary syndrome.

Why it happens

The exact cause of PCOS is unknown, but it often runs in families.

The condition is associated with abnormal hormone levels in the body, including having high levels of insulin.

Insulin is a hormone that controls sugar levels in the body. Many women with PCOS have too much insulin in their body, which contributes to the increased production and activity of hormones such as testosterone. Being overweight increases the amount of insulin your body produces.

Read more about the causes of polycystic ovary syndrome.

Treating polycystic ovary syndrome

There’s no cure for PCOS, but the symptoms can be treated. 

If you have PCOS and are overweight, losing weight and eating a healthy diet can help reduce some symptoms.

Medications are also available to treat symptoms such as excessive hair growth, irregular periods and fertility problems.

If fertility medications are ineffective, a simple surgical procedure called laparoscopic ovarian drilling (LOD) may be recommended. This involves using heat or a laser to destroy the tissue in the ovaries that’s producing androgens such as testosterone.

With treatment, most women with PCOS are able to get pregnant.

Read more about treating polycystic ovary syndrome.

The Map of Medicine is used by doctors throughout the NHS to determine the best treatment options for their patients. NHS Choices offers everyone in England exclusive and free access to this cutting-edge internet resource, which lets you see exactly what your doctor sees.

The information in the Map has been approved by the UK’s leading clinical experts, is based on the best available clinical evidence, and is continually updated. To take advantage of this unique resource go to:

Map of Medicine: polycystic ovary syndrome

The symptoms of polycystic ovary syndrome (PCOS) usually become apparent in your late teens or early twenties.

Not all women with PCOS have all of the symptoms. Each symptom can vary from mild to severe. In many women, the only symptoms are menstrual problems or a failure to conceive.

Common symptoms of PCOS include:

• irregular periods or no periods at all
• difficulty getting pregnant (because of irregular ovulation or failure to ovulate)
• excessive hair growth (hirsutism) – usually on the face, chest, back or buttocks
• weight gain
• thinning hair and hair loss from the head 
• oily skin or acne

You should talk to your GP if you have any of these symptoms and suspect you may have PCOS.

Fertility problems

Polycystic ovary syndrome is one of the most common causes of female infertility. Many women discover they have PCOS when they’re trying to get pregnant and are unsuccessful.

During each menstrual cycle the ovaries release an egg (ovum) into the uterus. This process is called ovulation and usually occurs once a month. Women with PCOS often fail to ovulate or ovulate infrequently, which means they have irregular or absent periods and find it difficult to get pregnant.

Risks in later life

Having PCOS can increase your chances of developing other health problems later in life. For example, women with PCOS are at an increased risk of developing:

• type 2 diabetes – a condition that causes a person’s blood sugar level to become too high
• depression and mood swings, as the symptoms of PCOS can affect your confidence and self-esteem
• high blood pressure and high cholesterol, which can lead to heart disease and stroke
• women who are overweight may also develop sleep apnoea – a condition that causes interrupted breathing during sleep

Women who have had absent or very irregular periods (fewer than three or four periods a year) for many years have a higher-than-average risk of developing cancer of the womb lining (endometrial cancer).

However, the chance of getting endometrial cancer is still small and can be minimised using treatments to regulate periods, such as the contraceptive pill or an intrauterine system (IUS).

Polycystic ovary syndrome (PCOS) can’t be cured, but the symptoms can be managed.

Treatment options can vary as someone with polycystic ovary syndrome (PCOS) may experience a range of symptoms, or just one.

The main treatment options are discussed in more detail below.

Lifestyle changes

In overweight women, the symptoms and overall risk of developing long-term health problems due to polycystic ovary syndrome (PCOS) can be greatly improved by losing excess weight. Weight loss of just 5% can lead to a significant improvement in PCOS.

You can find out if you are a healthy weight by calculating your body mass index (BMI), which is a measurement of your weight in relation to your height. A normal BMI is 19-25. Use the BMI calculator to work out if your BMI is in the healthy range.

You can lose weight by exercising regularly and having a healthy balanced diet. Your diet should include lots of fruit and vegetables, whole foods (such as wholemeal bread, wholegrain cereals and brown rice), lean meats, fish and chicken. Your GP can usually refer you to a dietician who can offer specific diet advice.

Read more about losing weight, healthy eating and exercise.

Medications

A number of medications are available to treat different symptoms associated with PCOS. These are described below.

Irregular or absent periods

The contraceptive pill may be recommended to induce regular periods or periods may be induced by progesterone tablets (which can be given regularly or intermittently). This will also reduce the long-term risk of developing cancer of the womb lining (endometrial cancer) associated with not having regular periods. An IUS (intrauterine system) will also reduce this risk but will not cause periods.

Fertility problems

With treatment, most women with PCOS are able to get pregnant.

Medications called clomifene and metformin are usually the first treatments used for women with PCOS who are trying to get pregnant. These medications encourage the monthly release of an egg from the ovaries (ovulation). You may be offered one of the medications or both together.

If you are unable to get pregnant despite taking clomifene and/or metformin, a different type of medication called gonadotrophins may be recommended. However, there’s a risk this medication may overstimulate your ovaries and lead to multiple pregnancies.

An alternative to gonadotrophins is a surgical procedure called laparoscopic ovarian drilling (see below). This treatment can be as effective as using gonadotrophins, but it does not increase your risk of multiple pregnancies.

It is likely that a fertility specialist will check that your fallopian tubes are not blocked before most of these treatments are used because this will prevent them from working.

Unwanted hair growth and hair loss

Medications to control excessive hair growth (hirsutism) and hair loss (alopecia) include:

• particular types of combined oral contraceptive tablets (such as co-cyprindiol, Dianette. Marvelon and Yasmin)
• cyproterone acetate
• spironolactone
• flutamide
• finasteride

These medications work by blocking the effects of “male hormones”, such as testosterone and some also suppress production of these hormones by the ovaries.

A cream called eflornithine can also be used to slow down the growth of unwanted facial hair. This cream doesn’t remove hair or cure unwanted facial hair, so you may wish to use it alongside a hair-removal product. Improvement may be seen four to eight weeks after treatment with this medication.

However, eflornithine cream is not always available on the NHS because some local NHS authorities have decided it is not effective enough to justify NHS prescription.

If you have unwanted hair growth, you will probably also wish to use a method of physically removing the excess hair (such as plucking, shaving, threading, creams or laser removal), although it is unlikely these will be provided on the NHS.

Other symptoms

Medications can also be used to treat some of the other problems associated with PCOS, including:

• weight-loss medication, such as orlistat, if you’re overweight
• cholesterol-lowering medication (statin), if you have high levels of cholesterol in your blood,
• acne treatments

Surgery

A minor surgical procedure called laparoscopic ovarian drilling (LOD) may be a treatment option for fertility problems associated with PCOS.

Under general anaesthetic, your doctor will make a small cut in your lower abdomen (tummy) and pass a long, thin microscope called a laparoscope through into your abdomen. The ovaries are then surgically treated using heat or a laser to destroy the tissue that’s producing androgens (male hormones).

Laparoscopic ovarian drilling has been found to lower levels of testosterone and luteinising hormone (LH) and raise levels of follicle-stimulating hormone (FSH). This corrects your hormone imbalance and can restore the normal function of your ovaries.