Hirsutism is caused by male sex hormones (chemicals produced by the body) called androgens. Androgens are present in all women, but those with hirsutism have either:
- an increased production of androgens, or
- an increased sensitivity to androgens
Androgens
There are several different types of androgens. The most well known is testosterone. In men, testosterone is involved in making sperm and in the development of male sexual characteristics, such as the voice getting deeper. Testosterone is also found in small amounts in women, where it may:
- increase your libido (sex drive)
- affect your menstrual cycle (your periods)
- affect your fertility
Testosterone levels may be normal in around half of all women with hirsutism.
Other androgens include:
- dehydroepiandrosterone
- androstenedione
These are precursors of testosterone, which means they will go on to become testosterone.
The causes of hirsutism varies in women, depending on whether they are premenopausal or menopausal.
These terms and the possible causes are explained below.
Premenopausal women
Premenopausal means before you have started the menopause (when a woman’s periods stop). There are a number of different causes that may explain hirsutism in premenopausal women.
Polycystic ovary syndrome (PCOS)
Almost three quarters of hirsutism cases in premenopausal women are caused by polycystic ovary syndrome (PCOS).
PCOS is a condition in which women have a number of small cysts (fluid-filled sacs) around the edge of their ovaries (the pair of reproductive organs that produce eggs and sex hormones in females). As well as causing excessive hair growth, PCOS can also cause:
- irregular periods
- weight gain
- acne
Many women with PCOS have an imbalance of male sex hormones, such as high levels of testosterone, but it is not known what causes this. See the Health A-Z topic about PCOS for more information about this condition.
Increased sensitivity
Just under a quarter of premenopausal women with hirsutism have normal androgen levels. It is thought that if your androgen levels are normal, your hirsutism may be caused by an increased sensitivity to the androgens.
This means that although you have the same amount of these hormones, you are extra sensitive to them and they have a bigger effect on your body.
Other causes
In a small number of cases, hirsutism in premenopausal women may be caused by:
- Cushing’s syndrome – a rare hormonal disorder that causes sudden weight gain and bloating around the chest and stomach
- congenital adrenal hyperplasia – an inherited condition that affects the adrenal glands (two glands above the kidneys that produce steroid hormones and male and female sex hormones)
- a tumour (growth) that produces androgens
- drugs – such as anabolic steroids (drugs that are often used illegally to build muscle and improve athletic performance)
- acromegaly – a hormonal disorder that causes the body to produce too much growth hormone, causing abnormal growth of the hand and feet
Menopausal women
Menopausal women are those who have started the menopause (when a woman’s periods stop) and have not had a period for a year. During the menopause, several of your body's hormones change, which can cause symptoms such as hot flushes.
In some women, as your hormone levels change, you will be left with a high amount of testosterone (an androgen), which can cause hirsutism. Hirsutism in post-menopausal women is also known as ovarian hyperthecosis.
See the Health A-Z topic about the Menopause for more information.
