Physiology and pathology of breast tissues are reviewed in term of hormonal regulation. The breast tissue enzymes activity and its regulation mechanism(s) – so called ”the intracrine concept” – are discussed. Additionally, the state of the art of the receptor mechanisms as well as epigenetic action of estrogen metabolites like catecholestrogens and its metabolites (2-hydroxy-, 4-hydroxy-, 16α-hydroxy-derivatives) with potential carcinogenic action is described. Data on perspectives of specific estrogen metabolites for clinical application and for epidemiological (screening) tests are also presented.