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Insulin-Like Growth Factor-1 Increases Breast Cancer Risk

Posted May 20 2010 7:04am
Insulin-like growth factor-1 (IGF-1) is a hormone produced naturally by our body, particularly in the liver.  This growth factor is involved in many processes related to growth and development.  Research over the last several years has reported that IGF-1 might increase a person's breast cancer risk; however, the reports have been inconsistent due to differences in study size and study design.

A new, large breast cancer study by the Endogenous Hormones and Breast Cancer Collaborative Group was conducted to more precisely determine the association between IGF-1, it's binding protein IGFBP-3, and breast cancer risk.  For this analysis, IGF-1 and IGFBP-3 blood level data from 17 studies that included nearly 5,000 breast cancer cases and over 9,000 controls was analyzed in relation to breast cancer risk.  The breast cancer researchers reported
  • IGF-1 levels were higher in moderately overweight women and in women who were moderate alcohol consumers.
  • Women whose IGF-1 blood concentrations were in the highest fifth had about a 28% increased risk for breast cancer compared to women in the lowest fifth.
  • The increased breast cancer risk was similar in both premenopausal and postmenopausal women.
  • Women with the highest levels of IGF-1 were 1.68 times more likely to develop estrogen receptor positive breast cancer; no increase in estrogen-receptor negative breast cancer was observed.
This new study clarifies the association between IGF-1 blood levels and breast cancer risk.  Overall, these results suggest that high circulating levels of IGF-1 increases breast cancer risk by about 30% irrespective of menopausal status with the risk being associated only with estrogen receptor-positive breast cancer.  While this new study gives us confirmation regarding the effect of IGF-1 on breast cancer risk, factors that modify this risk will remain an area of active investigation.  Another recent breast cancer study examined ethnic differences in IGF-1-associated breast cancer risk.  This study reported that IGF-1 substantially increased breast cancer risk in Caucasian women, but not in Hispanic women.  In contrast, IGFBP-3 increased breast cancer risk in both ethnic groups.  Future research will likely continue to explore the various factors that impact breast cancer risk associated with IGF-1 and its binding protein.

Some animal studies have reported that reduced calorie intake without malnutrition might reduce IGF-1 levels, though this effect is uncertain in human beings.  Read my book Fight Now: Eat & Live Proactively Against Breast Cancer to learn about more diet and lifestyle changes that can reduce your breast cancer risk.
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