Endocrine Abstracts

Natriuretic peptides BNP and NTpro-BNP have been suggested as being useful for the diagnosis of congestive heart failure, and have been shown to have excellent negative predictive value for excluding severe systolic left ventricular dysfunction.

We have shown previously that changes in thyroid function are associated with changes in concentrations of other low molecular weight molecules through the changes on renal function. Therefore, the aim of this study was to assess whether similar changes occurred with NT-proBNP concentrations following treatment of thyroid dysfunction.

Seventeen patients (12 female, 5 male, median age 51yrs, range 24-77) with newly diagnosed hypothyroidism and 21 patients (16 female, 5 male, median age 48yrs, range 21-66) with newly diagnosed hyperthyroidism had NT-proBNP measured at baseline and when they subsequently became euthyroid.

Heart failure was clinically excluded in all patients. The study was approved by the Local Ethics Committee and all patients gave their written informed consent.

Results. A Kolmogorov-Smirnov test showed that the data in both hypothyroid and hyperthyroid groups were normally distributed. The paired t-test was employed to compare the means before and after treatment.

The hypothyroid group showed a rise in NT-proBNP after treatment (mean plus/minus SD: 99.28 plus/minus 114.06 nanogram per litre vs 112.13 plus/minus 114.66, p=0.000). NT-proBNP levels did not differ in the hyperthyroid group though there was the suggestion of a trend towards lower concentrations after treatment (mean plus/minus SD: 100.68 plus/minus 118.29 nanogram per litre vs 82.02 plus/minus 83.31, p=0.082). However, these changes were within the expected wide range of biovariability of NT-proBNP shown in earlier studies.

Conclusion. Hypothyroidism decreases NT-proBNP concentrations, though this effect will be lost in the wide biovariability of natriuretic peptides, thus this statistically significant finding is likely not to be of clinical relevance.