Seven genetic markers linked with a woman's breast size have been keyed by researchers, claims a new study.
While it was known that breast size is in part heritable, this study is the first to find specific genetic factors that are associated with differences in breast size, the researchers said.
In addition, two of these markers have previously been associated with breast cancer risk.
According to Nicholas Eriksson of 23andMe, the genetic testing company that conducted the study, this suggests that some of the same biological pathways underlie both normal breast growth and breast cancer.
In the study, Eriksson and colleagues analyzed information from 16,175 female customers of European ancestry, and compared their answers to survey questions, including bra cup size and bra band size, to their genetic information.
While breast density is known to be a risk factor for breast cancer, the effect of breast size is less clear.
A few previous studies have found that larger breast size is associated with an increased risk of breast cancer in lean women.
The study has been published online in the journal BMC Medical Genetics.