Decreasing brain natriuretic peptide levels after treatment for hyperthyroidism.

BNP are produced in ventricular cardiomyocytes, and secreted in response to volume expansion or pressure overload. The purpose of this study was to assess BNP levels in patients with hyperthyroidism before specific treatment for hyperthyroidism and after euthyroidism was achieved. The study was performed in a prospective design. The study population consisted of 48 consecutive newly diagnosed untreated overt hyper-thyroid patients who had not been treated any anti-thyroid medications before. All subjects underwent transt-horacic echocardiography. Levels of fT3, fT4, TSH and BNP were measured before the onset of the treatment and after euthyroidism was achieved. A significant decrease in BNP (102.5 (6.7-1769) ng/L vs. 5.0 (0.1-87.0) ng/L p< 0.001) levels were observed, after euthyroidism was achieved. The decrease in BNP levels was posi-tively correlated with the decrease in fT3 (r=0.298; p=0.049) and fT4 (r=0.313; p=0.030). There was no cor-relation between BNP levels and TSH levels (p=NS). We conclude that hyperthyroidism may cause high BNP measurements which can lead to misdiagnosis of congestive heart failure. We suggest that thyroid hormones should be checked in patients with high levels of BNP.