N-terminal-pro-B-type natriuretic peptide in acute hyperthyroidism

Hemodynamic changes in neonates born to mothers with Graves' disease

PURPOSE

Cardiac insufficiency is a major morbidity in neonatal hyperthyroidism. It is important to assess the hemodynamics in neonates born to mothers with Graves' disease (GD). This study prospectively evaluated the hemodynamic changes in neonates born to mothers with GD.

METHODS

Overall, 80 newborns were enrolled. Thirty-six neonates were born to mothers with GD who were positive for thyroid-stimulating hormone (TSH) receptor antibody (TRAb), and 44 were born to mother negative for TRAb. The serum levels of TSH, free triiodothyronine (FT₃), free thyroxine (FT₄), and N-terminal-pro-B-type natriuretic peptide (NT-proBNP), the cardiac output, and cardiac index (CI) evaluated by echocardiography were compared between the two groups at several postnatal points (day of delivery and 5, 10, and 30 days of life).

RESULTS

The TRAb-positive newborns had higher FT₄ levels and CI on Day 5 (both p < 0.05) and higher FT₃ (p < 0.05) and FT₄ levels (p < 0.01) and CI (p < 0.01) but lower TSH levels (p < 0.05) on Day 10 than the TRAb-negative newborns. The TRAb-positive newborns had significantly higher NT-proBNP levels on Days 5 (median 752 vs. 563 pg/mL, p = 0.034) and 10 (median 789 vs. 552 pg/mL, p = 0.002) than the TRAb-negative newborns.

CONCLUSIONS

Hemodynamic changes in neonates born to TRAb-positive mothers with GD resulted in a higher CI and NT-proBNP levels than in those with TRAb-negative mothers from postnatal days 5 to 10.

β1-adrenergic and Muscarinic Acetylcholine Type 2 Receptor Antibodies are Increased in Graves' Hyperthyroidism and Decrease During Antithyroid Therapy

OBJECTIVE

To determine the association between autoantibodies to G-protein-coupled receptors with effect on the cardiovascular system and the cardiac biomarker N-terminal pro-brain natriuretic peptide reflecting heart function in Graves' disease.

DESIGN AND METHODS

Sixty premenopausal women with Graves' disease were analyzed for IgG autoantibodies against β₁-adrenergic, muscarinic acetylcholine type 2 and angiotensin II type 1 receptors using enzyme-linked immunosorbent assays based on cell membranes overexpressing receptors in their native conformations. N-terminal pro-brain natriuretic peptide and heart symptoms were analyzed in hyperthyroidism and after 7.5 months of antithyroid treatment. Matched thyroid healthy controls were also assessed.

RESULTS

Serum levels of antibodies against the β₁-adrenergic and the muscarinic acetylcholine type 2 receptors were higher in hyperthyroid patients than in controls (median β₁-adrenergic receptor antibodies 1.9 [IQR 1.3-2.7] vs. 1.1 [0.8-1.7] μg/mL, P<0.0001; muscarinic acetylcholine type 2 receptor 20.5 [14.0-38.3] vs. 6.0 [3.2-9.9] U/mL, P<0.0001). These antibodies decreased in euthyroidism (P<0.01), but were still higher than in controls (P<0.01). Angiotensin II type 1 receptor levels did not differ. N-terminal pro-brain natriuretic peptide was higher in hyperthyroidism (240 [134-372] vs. <35 [<35-67] ng/L, P<0.0001), normalized after treatment and did not correlate with autoantibodies.

CONCLUSION

Autoantibodies against the β₁-adrenergic and the muscarinic acetylcholine type 2 receptors were increased in Graves' patients, decreased with treatment, but did not correlate with cardiac function. However, an autoimmune effect on the heart cannot be excluded in subpopulations, as the functional properties of the analyzed antibodies remain to be determined.

Relationships between serum levels of thyroid hormones and serum concentrations of asymmetric dimethylarginine (ADMA) and N-terminal-pro-B-type natriuretic peptide (NT-proBNP) in patients with Graves' disease

Endothelial dysfunction as well as abnormal thyroid hormone levels may be responsible for increased cardiovascular risk in Graves' disease (GD). Asymmetric dimethylarginine (ADMA) and N-terminal-pro-B-type natriuretic peptide (NT-proBNP) are new markers of endothelial and myocardial dysfunction, respectively. The purpose of this study was to investigate the relationship among the serum levels of ADMA, NT-proBNP, and thyroid hormones in GD patients. This was a cross-sectional investigation conducted in a university teaching hospital. Two hundred and thirty-nine GD (Female: 182, Male: 57) patients and 81 normal controls were enrolled in this study. Serum levels of ADMA were positively related with FT3 (r = 0.584, P < 0.001), FT4 (r = 0.551, P < 0.001), and TRAb levels (r = 0.502, P < 0.001). Serum NT-proBNP levels were positively associated with FT3 (r = 0.243, P < 0.001) and FT4 levels (r = 0.274, P < 0.001), as well as heart rate (r = 0.271, P < 0.03). The elevation of serum ADMA and NT-proBNP levels were also observed in patients with controlled hyperthyroidism. It is thus concluded that serum ADMA and NT-proBNP levels were increased in GD patients. Future studies may determine the usefulness of these two biomarkers to detect early signs of endothelial dysfunction, vascular stiffness, and fluid volume in GD patients.

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.