Recent research revealed that higher-than-normal levels of insulin increase the risk of breast cancer in postmenopausal women.

Research team led by Marc Gunter and Howard Strickler, of the Albert Einstein College of Medicine in New York studied the association between incident breast cancer and baseline fasting insulin, insulin-like growth factor-1 (a related hormone), and oestradiol levels in 835 women enrolled in the Women's Health Initiative Observational Study who developed breast cancer along with a randomly-selected sample of 816 women in the study who did not develop breast cancer.

The study subjects were divided into four groups based on their fasting insulin levels. Data analysis revealed that the subjects with the highest insulin levels had a 1.5-fold higher risk of developing breast cancer as compared to those with the lowest insulin levels.

The researchers analyzed women who were not using hormone therapy separately. Data analysis revealed that individuals with the highest insulin levels had a 2.4-fold increased risk of developing breast cancer than those with the lowest levels.

Researchers said that the data suggests that hyperinsulinemia is an independent risk factor for breast cancer and may have a substantial role in explaining the obesity-breast cancer relationship.