The role of local estrogen biosynthesis in males and females

Natural (human) and experimental (mouse) models of estrogen insufficiency h ave revealed hitherto unexpected roles for estrogens in both males and fema les. In postmenopausal women, and in men, estrogen no longer has a major ro le as a circulating hormone, but rather it functions locally as a paracrine or even 'intracrine' factor in tissue sites where it is formed. As a conse quence, the tissue-specific nature of aromatase production assumes physiolo gical and pathophysiological significance. The availability of circulating precursors is also important in sites where there is no local supply of C-1 9 precursors, particularly in elderly women. The potential clinical signifi cance of these findings in terms of the development of new therapeutic moda lities is discussed.