The maintenance of arterial blood pressure and the distribution of blood
flow to the various organs of the body depends on the control of the
pumping action of the heart and of the resistance of the vascular beds
in the individual organs in accordance with their metabolic needs. These
controls are achieved through the integrated actions of circulat- ing
hormones, humoral factors that are synthesized and released in the heart
and blood vessels, and the autonomic nervous system. The heart, however,
is not only the target for the direct and indirect actions of a number
of hormones and humoral factors, it is also an endocrine organ 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.
