NPPB (Natriuretic peptide B) is a member of the natriuretic peptide family and encodes a secreted protein which functions as a cardiac hormone. The protein undergoes two cleavage events, one within the cell and a second after secretion into the blood. The protein's biological actions include natriuresis, diuresis, vasorelaxation, inhibition of renin and aldosterone secretion, and a key role in cardiovascular homeostasis. A high concentration of NPPB in the bloodstream is indicative of heart failure. NPPB also acts as an antimicrobial peptide with antibacterial and antifungal activity. Mutations in NPPB have been associated with postmenopausal osteoporosis.