This summary table contains detailed information about research studies. Summary tables are a useful way to look at the science behind many breast cancer guidelines and recommendations. However, to get the most out of the tables, it’s important to understand some key concepts. Learn how to read a research table.
Introduction: Prolactin is a natural hormone in the body. It plays a role in breast growth and the production of milk during breastfeeding.
Women with higher blood levels of prolactin have a slightly higher risk of breast cancer than women with lower levels.
Learn more about prolactin 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: Prospective nested case-control studies with at least 100 breast cancer cases and meta-analyses.
Table note: Relative risks above 1 indicate increased risk. Relative risks below 1 indicate decreased risk.
Study Population(number of participants)
Risk of Breast Cancer in Women with Higher Blood Prolactin Levels Compared to Women with Lower Levels Relative Risk (95%CI)
Nested case-control studies
EPIC cohort 
Nurses’ Health Study and Nurses’ Health Study II 
KARMA study 
Malmo Diet and Cancer Study and Northern Sweden Health and Disease Study 
Wang et al. 
Wang et al. 
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