BNP (Brain natriuretic peptide) is a member of the natriuretic peptide family and encodes a secreted protein which functions as a cardiac hormone. BNP is a 32 amino acid polypeptide and is co-secreted along with a 76 amino acid N-terminal fragment which is biologically inactive. This protein has biological actions including natriuresis, diuresis, vasorelaxation, inhibition of renin and aldosterone secretion.