Steroids and the risk of breast cancer

The search for major abnormalities as causes for breast cancer have not been successful, whether they have been directed to patients with this disease, different groups, or populations at risk. Anovulation or progesterone deficiency are not characteristic for those at risk for breast cancer or those patients with early breast cancer. In contrast, early-onset long-lasting ovulatory cycle function seems to be prevalent in different risk categories. Women with early menarche are additionally characterized by having higher serum estradiol and lower sex hormone-binding globulin concentrations than women with later menarche, at least during the early years of their fertile life. Estradiol is a central agent in the process of breast cancer appearance, and progesterone does not seem to have an opposing action. A decrease in the number of ovulatory cycles may exert a protective effect against breast cancer. If the decrease is affected by endocrine mechanisms maintaining breast ethelial stimulation comparable to that during the normal menstrual cycle, the protective effect would be nullified.