INTRACRINOLOGY

A large proportion of androgens in men (40%), and the majority of estrogens in women (75% before menopause and close to 100% after menopause), are synthesized in peripheral target tissues from precursor steroids of adrenal origin. The genes encoding the formation and metabolism of androgens and estrogens are expressed in a large series of peripheral tissues, thus providing the basis for a promising new area in hormone action, namely intracrinology. These steroidogenic and steroid metabolizing enzymes should become a major target of novel therapies for steroid-sensitive diseases, particularly breast and prostate cancer.