Circulating Natriuretic Peptides Concentrations in Hyperthroid Cats

Klein A., Pace C., Elliott J., et al.

Conference Proceedings, (2010). American College of Veterinary Internal Medicine, Anaheim: p.730

The cardiac biomarkers N-terminal-pro-Brain Natriuretic Peptide (NT-pro-BNP) and N-terminal -pro-Atrial Natriuretic Peptide (NT-pro-ANP) have been shown to be of value in the diagnosis of heart disease and heart failure in cats. In humans, it is well known that natriuretic peptides are influenced by factors other than pri- mary cardiovascular disease, including hyperthyroidism. The purpose of this study was to investigate natriuretic peptide concentrations in hyperthyroid cats before and after anti-thyroid treatment and to compare them to normal cats. Hyperthyroid cats were recruited from two first opinion clinics in central London. All cats received a full physical examination, plasma biochemistry, total thyroxine (tT4), PCV and systolic blood pressure (SBP; Doppler technique) measurement. Hyperthyroid cats (tT4 4 55 nmol/l) were treated medically and/or surgically and cats achieving euthyroid status (tT4 o 40 nmol/l) were selected for inclusion in the study. A control population of old (4 9 years) normal euthyroid cats (n 5 21) was also selected. NT-pro-ANP and NT-pro-BNP were assayed retrospectively on stored samples (VETSIGN Feline Cardio-SCREEN proBNP; Guilday Ltd. and proANP (1–98); Biomedica). The sample population was compared to normal euthyroid cats by using a Mann-Whitney test. Spearman’s rho was determined to evaluate potential associations between heart rate, tT4, creatinine, SBP and natriuretic peptide concentrations. A Wilcoxon signed-rank test was used to compare circulating natriuretic peptides and other clinical parameters before and after treatment. Results are reported as median [25th, 75th percentile]. Eighty four cats were enrolled in the study. When compared to control euthyroid cats, hyperthyroid cats had significantly higher NT-pro-BNP (205.05 [69.7, 369.8] vs. 30 [12.2, 42.2] pmol/L, p o 0.0001) but not NT-pro-ANP concentrations. A significant association was found only between NT-pro-BNP concentration and tT4 (r 5 0.29, p 5 0.01) but not with any other parameter. A significant difference in NT-pro-BNP concentration (205.05 [69.7, 369.8] vs. 100.8 [58.5, 248.9] pmol/L, p o 0.0001), tT4 (152.7 [91.5, 173.3 vs. 20.6 [4.7, 19.4] nmol/L, p o 0.0001), heart rate (200 [190, 240] vs. 180 [160, 192] min?1, p o 0.0001), creatinine (98.5 [80.05, 120.2] vs. 136.7 [110.5, 161] mmol/L, p o 0.0001) and PCV (35 [34, 40] vs. 33 [32, 38]%, p 5 0.002) was found before and after treatment. These findings demonstrate that hyperthyroid cats may have elevated NT-pro-BNP but not NT-pro-ANP concentrations com- pared to normal cats and that NT-pro-BNP but not NT-pro-ANP concentrations decrease following anti-thyroid treatment. Thyroid status should be taken into account when interpreting circulating NT-pro-BNP concentrations in cats.