in the traditional sense, synthesizing and secreting into the circulation chemical factors that act at distant sites. In this treatise, Hormones and the Heart in Health and Disease, we interpret "endocrinology" broadly and consider traditional hormones as well as autocoids that are secreted by the heart or that act on it. In this overview, the relevant chapters are indicated in parentheses. The discovery of atrial natriuretic peptide (ANP; atrial natriuretic factor, ANF) in the 1980s indicated that the heart does indeed function as an endocrine organ in the classic sense. ANP (Chapter I) is synthesized in the heart and secreted into the circulation for actions on the kidney, where it is a potent natriuretic agent, and on the vasculature, where it causes vasodilation. ANP can also affect myocardial contractility.