NPPB and hyperthyroidism: Laboratory data at presentation revealed an elevated N-terminal prohormone of brain natriuretic peptide (NT-proBNP) level of 2,122 pg/mL (reference, ≤125 pg/mL), but showed no evidence suggestive of underlying etiology for heart failure, such as ischemic or inflammatory changes, hypokalemia, or hyperthyroidism.