We don’t know the exact cause of PCOS, but genetics has an important role, and family history is also important. PCOS is commonly associated with increased levels of two hormones in the body, insulin and androgens (male-type hormones).
The symptoms of PCOS include excess hair growth (hirsutism), scalp hair loss, acne, irregular or infrequent periods, weight gain, difficulties with fertility and increased anxiety and depression. Not every woman with PCOS will have every symptom, and each woman will be individual in her experience. Symptoms can also change during the course of a woman’s life.
Polycystic ovary (ovarian) syndrome (PCOS) is the most common hormonal disorder in women of reproductive age (the time from when a woman’s periods begin to when they stop at menopause). It affects 8-13% of women – about one in 10 – in this age group, and can affect more in some high-risk groups, such as Indigenous, Asian, North African and Caucasian European women.
Hormones are chemicals made in your body that carry messages through your bloodstream. They help control many functions in your body, such as growth, energy, sexual function, reproduction, digestion and temperature.
In a woman with PCOS, her body has an imbalance of two hormones, insulin and androgens. The higher levels of these hormones are responsible for the symptoms and signs of PCOS.
The name ‘polycystic ovary syndrome’ is a bit misleading: it suggests the problem is mainly with the ovaries, and that you might have multiple ‘cysts’ on your ovaries. However, the cause of PCOS is hormonal: it is not a problem that affects just the ovaries, as the name might suggest.
It is thought that increased levels of insulin in the body cause the ovaries to work differently, which then produce excessive levels of male-type hormones (androgens), which in turn cause many of the symptoms of PCOS. If the hormone levels can be controlled, the ovaries often function normally, and symptoms improve.
The ovaries are small, oval-shaped organs located in the pelvis. Their main job is to help women to get pregnant. They produce an egg each month. When the egg is mature, it is released from the ovary (ovulation) and pushed down the fallopian tube so it can be fertilised.
In women with PCOS, the eggs do not develop fully. This is the main cause of difficulties with getting pregnant.
In some women diagnosed with PCOS, an ultrasound image of their ovaries will show multiple follicles in the ovaries: these are not actually cysts, but partially formed eggs within the ovaries that haven’t developed properly. They are caused by the increased levels of male-type hormones in the body. It is good to note that there is no known link between these follicles (or under-developed eggs) in the ovaries of women with PCOS and either larger true ovarian cysts (that sometimes need surgery) or the risk of ovarian cancer.
The female reproductive system
The exact cause of PCOS is unknown, but there do seem to be connections with family history and genetics; hormones that are increased during our development in the womb before birth; and lifestyle or environment.
So far, no single gene has been found to cause PCOS, so the link is likely to be complex and involve multiple genes.
Women with PCOS are 50% more likely to have an immediate female relative – mother, aunt, sister or daughter – with PCOS. Type 2 diabetes is also common in families of those with PCOS.
An imbalance in the body of the hormones insulin and androgens (male-type hormones, such as testosterone) causes the symptoms and signs of PCOS.
One of the roles of insulin in the body is to keep levels of glucose (sugar or energy) in the blood from rising too high after eating. It does this by ‘unlocking’ the body’s cells and allowing glucose to pass from the blood into the cells. This brings down the levels of glucose in the blood.
Around 85% of all women with PCOS have ‘insulin resistance’. If you are insulin resistant, your body’s cells stop responding normally to insulin, and instead block the entry of glucose into the cells. This means your body doesn’t use the available insulin effectively to help keep your glucose levels stable.
Because the insulin is not working effectively, the body reacts by producing more insulin. Higher levels of insulin increases the production of androgens, such as testosterone, in the ovaries.
Insulin resistance is caused in part by lifestyle factors – including being overweight, because of diet or physical inactivity. But insulin resistance can also be caused by genetic factors and can occur in women of all weight ranges. Evidence shows that in women with PCOS, about 95% of those with unhealthy weight and about 75% of those who are lean, have insulin resistance.
Insulin resistance plays a large role in the symptoms of PCOS, so it is important to understand what it is. But it is also important to know that there are ways to reduce it.
Regular activity and healthy eating are very important in managing and reducing insulin resistance and can greatly improve the symptoms of PCOS.
Androgens, sometimes known as ‘male hormones’, are normally present in both men and women, but at much lower levels in women. All women produce small amounts of androgens in body tissues, including in the ovaries and the adrenal glands. Increased levels of androgens in women with PCOS cause symptoms such as excessive body hair growth, scalp hair loss and acne. They also contribute to symptoms such as irregular periods and irregular ovulation.
PCOS can occur in both slender and overweight women. However, women with PCOS are at greater risk of being overweight or obese.
Being above a healthy weight worsens insulin resistance, which is also thought to be a key part of the development of PCOS, and the symptoms of PCOS. Excess weight increases both the hormones responsible for PCOS symptoms.
The good news is that a healthy lifestyle of nutritious food and physical activity can help to treat PCOS and improve the symptoms.
Support is available to help you make lifestyle changes that will benefit your overall health, including many of the symptoms of PCOS. For more information, see our pages on Healthy living.
Factors contributing to the development of PCOS
PCOS symptoms present in many different ways. Some women will have only some, or mild symptoms, whereas others will have a number of severe symptoms. Symptoms can also change at different stages of a woman’s life.
Symptoms of PCOS may include:
|Periods & fertility||
No periods, or periods that are:|
Immature ovarian eggs that do not ovulate
Multiple 'cysts' on the ovaries
Difficulty becoming pregnant
Some health challenges during pregnancy
|Hair, skin & body||
Excess facial and/or body hair (hirsutism)|
Scalp hair loss (alopecia)
Acne on the face and/or body that can be severe
Darkened skin patches (acanthosis nigricans)
|Mental & emotional health||
Poor body image
Impact on quality of life
|Related health conditions||
Sleep apnoea (a sleep disorder in which abnormal pauses of breathing occur during sleep)|
Increased risk of diabetes, with earlier onset
Sexual health challenges
Increased risk of cardiovascular disease
Read more on PCOS in our booklet 'Understanding polycystic ovary syndrome: All you need to know'
Although some women with PCOS have regular periods, high levels of androgens and insulin can disrupt the monthly cycle of ovulation (when eggs are released) and menstruation.
If you have PCOS, your periods might be irregular, or stop altogether. In some girls, PCOS is a cause of periods failing to start.
The average menstrual cycle is 28 days with one ovulation, but anywhere between 21 and 35 days is considered normal.
As menstrual cycles lengthen, ovulation can stop entirely (called ‘anovulation’) or occur only occasionally. Some women with PCOS also experience heavier or lighter bleeding during their cycle.
Learn more about irregular periods and management here.
It is important to know that women with PCOS have the same number of children (with or without assistance) as women without PCOS. Many women with PCOS have children without the need for infertility treatment but some women will require medical assistance to help them get pregnant.
In women with PCOS, high levels of androgens and insulin can affect the menstrual cycle and prevent ovulation (the release of a mature egg from the ovary). Ovulation can stop completely (anovulation), or it can occur irregularly. This can make it more difficult for women with PCOS to become pregnant naturally, however, this does not mean that all women with PCOS are infertile. Women with PCOS can also have a greater risk of pregnancy complications once they are pregnant.
Read more on fertility management here.
‘Hirsutism’ is excess hair growth on the face and body due to high levels of androgens stimulating the hair follicles. This excess hair is thicker and darker than normal. The hair typically grows in areas where it is more usual for men to grow hair, such as the sideburn region, chin, upper lip, around the nipples, lower abdomen, chest and thighs.
Up to 60% of women with PCOS have hirsutism. Women with PCOS from ethnic groups prone to darker body hair (eg, Sri Lankan, Indian and Mediterranean populations) often find they are more severely affected by hirsutism.
For some women with PCOS, the high level of androgens causes hair loss or thinning of the scalp hair in a ‘male-like' pattern: a receding frontal hairline and thinning on top of the scalp.
If you have PCOS, the higher level of androgens can increase the size of the oil production glands on the skin, which can lead to increased acne. Acne is common in adolescence, but young women with PCOS also tend to have more severe acne.
Women with PCOS can also develop skin tags, which are thickened lumps of skin that typically occur in the armpits, on the neck or along the bra line.
Rough, dark, velvety patches of skin can also develop in women with PCOS. These occur in the armpits or neck area, and are called acanthosis nigricans.
These symptoms can be very distressing for some women, but treatments are available to help with them all.
Learn more on hair & acne management here.
Depression and anxiety are common symptoms of PCOS. It is not clear why women with PCOS have an increased risk of emotional challenges. There might be a link to the hormonal changes that occur in PCOS, but more research is needed in this area before we can understand why and how the hormones affect mental wellbeing in PCOS.
Coping with hirsutism, severe acne, weight changes and fertility problems can affect your body image, self-esteem, sexuality and femininity. This can add to depression and anxiety levels. Problems with fertility can have an impact on your mood, particularly if fertility has been a concern for a long time.
In addition, these emotional challenges can be particularly difficult if you are unaware that you have PCOS. A delayed diagnosis of PCOS, as well as problems with weight management, can make you feel discouraged and helpless. This is especially so if you do not have the knowledge and support you need to manage these symptoms. This creates a negative cycle, making it harder to take charge of your health and live the healthiest lifestyle you can.
The emotional challenges of PCOS can be very difficult, but with the right support, education about PCOS, and appropriate treatment, your emotional and physical health can be improved.
Read more on the Emotions webpage.