Many females experience a small amount of breast tissue development caused by hormones circulating in their bloodstream. (dogs.lovetoknow.com)
I never felt any breast pain or had much change in breast tissue with either pregnancy. (babycenter.com)
We observed a significant positive association between testosterone and breast density, particularly because of a positive association with the absolute amount of dense breast tissue. (cebp.aacrjournals.org)