BNP is mainly expressed by the ventricular myocardium in response to volume overload and increased filling pressure. It is synthesized and secreted by cardiomyocytes. Mature BNP consists of 108 amino acids (proBNP or BNP-108). ProBNP is cleaved during secretion in a 1:1 ratio resulting in physiologically active BNP-32 and the biologically inactive 76 amino acid NT-proBNP (http://www.uniprot.org/uniprot/P16860#PRO_0000001532). NT-proBNP (1-76) has greater plasma stability and a much longer biological half-life (90-120 minutes) than BNP, being considered as the preferred laboratory marker.