Androgens are male hormones (such as testosterone). All women produce a small amount of male hormones in tissues including the ovaries and the adrenal gland on the kidneys. These male hormones are converted into oestrogen which has functions in puberty and during menstruation.

One of the main symptoms of PCOS is excessive androgen production (i.e. high levels of male hormones). This can cause a variety of effects on the body, including:

• Irregular ovulation (release of mature egg from the ovary)
• Irregular menstrual cycle
• Physical symptoms (e.g. acne, excess hair etc.)

The effect of androgens on the ovary

In the ovaries, high levels of androgens can prevent ovulation and can affect the menstrual cycle. In a normal menstrual cycle, one egg matures and is released each month through ovulation. The ‘cysts' seen in polycystic ovaries are the follicles or eggs that have matured but were not released at ovulation. Instead, they stay in the ovary, giving the appearance of multiple small cysts.

On an ultrasound, the diagnosis of polycystic ovaries is confirmed if there are 12 or more follicles visible on one ovary or if the size of one or both ovaries is increased. This can be done through an abdominal ultrasound or a vaginal ultrasound. Women with PCOS can ovulate regularly, ovulate irregularly or some may not ovulate at all.

The effect of androgens on the menstrual cycle

The effect of androgens on the menstrual cycle differs from woman to woman. Some women can have no menstrual cycle (amenorrhoea) or some may have fewer periods due to a longer menstrual cycle, i.e. more than the standard 28 day cycle.

Physical effects of high androgen levels

High levels of androgens can also spill over into the blood and act on other tissues in the body.  This can lead to symptoms such as excessive hair growth (hirsutism), acne, scalp hair loss (alopecia) or darkened skin patches (acanthosis nigricans).

For more information, see Symptoms.

Content updated 25 August 2011