This summary table contains detailed information about research studies. Summary tables offer an informative look at the science behind many breast cancer guidelines and recommendations. However, they should be viewed with some caution. In order to read and interpret research tables successfully, it is important to understand some key concepts. Learn how to read a research table.
Introduction: Insulin-like growth factor-1 (IGF-1) is a natural hormone in the body. It plays an important role in growth and development.
Although it is vital to human health, there is a growing body of evidence that IGF-1 may be linked to breast cancer. Results from two large nested case-control studies and two pooled analyses suggest higher blood levels of IGF-1 may increase the risk of breast cancer in premenopausal women. However, the data overall are mixed. Much more research is needed to understand the role that IGF-1 and similar hormones (like prolactin) may play in breast cancer development.
Another issue is the current lack of a standard for analyzing the blood levels of hormones like IGF-1. Until there is an agreed-upon standard measure, the results from future studies are likely to remain mixed.
Learn more about IGF-1 and breast cancer risk.
Learn about the strengths and weaknesses of different types of studies. See how this risk factor compares with other risk factors for breast cancer. Study selection criteria: Nested case-control studies with at least 300 breast cancer cases and pooled analyses. Table note: Relative risk above 1 indicates increased risk. Relative risk below 1 indicates decreased risk.
Study Population(number of participants)
Relative Risk of Breast Cancer in Women with Higher versus Lower IGF-1 Levels, RR (95% CI)
Nested case-control studies
Women’s Health Initiative Observational Study 
Nurses' Health Study II 
Kaaks et al. 
Melbourne Collaborative Cohort Study 
Gronbaek et al. 
Nurses' Health Study 
Vatten et al. 
Renehan et al. 
Shi et al. 
Sugumar et al. 
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