A new study has reported that high circulating glucose and insulin resistance both increase the risk of breast cancer. The study included women in the prospective Hormones and Diet in the Etiology of Breast Tumors (ORDET) study who gave blood samples during the period 1987 to 1992. The authors assessed associations between breast cancer risk with and serum fasting glucose, insulin, homeostasis model assessment-insulin resistance (HOMA-IR) index, and sex hormone-binding globulin. Sex hormone-binding globulin has been reported to be inversely associated with risk of breast cancer. After a median follow up period of 13.5 years, 356 women had been diagnosed with breast cancer. Four matched controls per breast cancer case were used as comparison.

Women in the highest fourth of fasting glucose levels were found to have significantly higher risk of breast cancer than those in the lowest glucose quartile. The association held for both premenopausal and postmenopausal women when analyzed separately and in women diagnosed after 55 years of age. Women in the highest insulin resistance quartile also were found to have higher risk of breast cancer than the lowest quartile. Significantly increased breast cancer risk was also found in women who were diagnosed after 55 years of age and who were in the highest insulin resistance quartile when these women were analyzed separately; in the same group decreased breast cancer risk was significantly associated with high sex hormone-binding globulin. The authors comment that the study results add to the existing epidemiological evidence that hyperglycemia and insulin resistance increase breast cancer risk.

Please see our article on type 2 diabetes and breast cancer for more information on the relationship between glucose metabolism and breast cancer.