Ovarian steroids and control of proliferation in the normal human breast

Until recently, there has been considerable uncertainty as to how, or even which of the ovarian steroids influence human breast luminal epithelial cell proliferation. It is important that this is known because increased proliferative activity of this particular cell population is associated with increased risk of breast cancer. Review of the available literature suggests that while oestradiol is the major steroid mitogen in pre-menopausal women, the role of progesterone becomes more significant after the menopause when oestradiol levels are reduced. Moreover, recent studies have given new insights into the mechanisms by which oestradiol and progesterone exert their effects. This knowledge may allow development of new strategies for predicting breast cancer risk or preventing the disease.