B-type natriuretic peptide (BNP) is a hormone produced by your heart. N-terminal (NT)-pro hormone BNP (NT-proBNP) is a non-active prohormone that is released from the same molecule that produces BNP. Both BNP and NT-proBNP are released in response to changes in pressure inside the heart. These changes can be related to heart failure and other cardiac problems. Levels goes up when heart failure develops or gets worse, and levels goes down when heart failure is stable. In most cases, BNP and NT-proBNP levels are higher in patients with heart failure than people who have normal heart function.