What is insulin resistance?

Insulin resistance is a state where the body can’t carry out the normal actions of insulin. One of the roles of insulin is to keep the levels of glucose in the blood stable. In women with polycystic ovary syndrome (PCOS), high levels of insulin can increase the production of male hormones (androgens such as testosterone) in the ovaries. This contributes to symptoms such as menstrual irregularity, difficulty in ovulating, excessive hair growth and acne. Up to 80 per cent of women with PCOS have some form of insulin resistance. This can be associated with a genetic cause, a lifestyle cause (e.g. being overweight or inactive) or usually a combination of both.

Treating insulin resistance

Treatment for PCOS can either focus on treating the symptoms or treating the cause of the symptoms. As insulin resistance is so common in women with PCOS and causes many of the symptoms of PCOS, treating it is one way to treat PCOS. This can be done through weight loss, diet and physical activity and through medications which improve insulin resistance (insulin sensitising agents). Lifestyle change is the first line treatment (see Lifestyle Management), but in many cases, medical management may also be needed.

Medical management

Medications that reduce insulin resistance have the added benefit of a reduction in the risk of developing type 2 diabetes and cardiovascular disease in the long-term. Medications that lower insulin in the blood include:

• Metformin  (sold as e.g. Glucophage)
• Glitazones, e.g. rosiglitazone (sold as Avandia), pioglitazone (sold as Actos) - not recommended in PCOS

These medications are also used to treat type 2 diabetes. In women with PCOS, metformin can improve risk factors for cardiovascular disease and diabetes such as cholesterol and glucose levels and inflammatory hormones.

Metformin

In normal weight or overweight women with PCOS, metformin has been shown to be successful in:

• Reducing insulin resistance
• Reducing high male hormone levels
• Reducing excessive hair growth or acne
• Improving menstrual regularity , ovulation and pregnancy rates
• Reducing the risk of diabetes in those at high risk

There is some evidence that metformin can assist in weight loss and preventing weight gain. 

Possible side effects

Some women who take metformin have some temporary gastrointestinal side effects (nausea, abdominal bloating, vomiting and loss of appetite). Metformin treatment can be started at lower doses to reduce the severity of these side effects. There are currently no guidelines as to the use of metformin during pregnancy. The slow release form of metformin, taken at night, has less severe side effects than standard metformin treatment. Metformin has been in use for around 60 years and is a drug with few serious side effects. Rarely (in elderly people, or those with liver or kidney failure), it can cause serious side effects Note: Metformin is not approved for use in Australia as yet, as no approval application has been lodged, although the application process for approval is underway.

Glitazones

Glitazones are generally as effective as metformin for treating menstrual irregularity and infertility in PCOS. Rosiglitazone has been associated with a higher number of cardiovascular events than pioglitazone and has been recommended to be removed from the New Zealand, European and United Kingdom markets. These agents have been trialled in PCOS, but they are not recommended as they can have significant side-effects. Glitazones should not be used during pregnancy.  

Content updated 25 August 2011