When proBNP (brain natriuretic peptide) is released from cardiomyocytes in response to stretch, it’s cleaved into biologically active BNP and inert NT-proBNP in equal amounts. NT-proBNP, with its longer half-life (70 vs. 22 minutes), circulates at higher levels. Elevated concentrations of either biomarker can help diagnose heart failure, and a reduction over time usually reflects improved management in chronic heart failure patients. MedThreads