Endogenous steroids in the pathophysiology of breast cancer.

The search for major endocrine abnormalities as causes for breast cancer has not been successful, whether it has been directed at patients with this disease or at different groups or populations at risk. An early-onset, long-lasting ovulatory cycle function seems to be prevalent in different risk categories for breast cancer. Women with early menarche, compared with those with late menarche, are additionally characterized as having higher circulating estradiol and lower sex-hormone-binding globulin concentrations. A number of additional findings point to estradiol as a central agent in the development of breast cancer, and cyclic progesterone secretion does not seem to have a clearly opposing action.