Serum Symmetric Dimethylarginine Concentrations in Hyperthyroid Cats With and Without Azotemic Chronic Kidney Disease

Williams T.

American College of Veterinary Internal Medicine 2017.

Hyperthyroidism decreases body muscle mass and serum creatinine concentrations which can confound diagnosis of concurrent chronic kidney disease (CKD). Serum symmetric dimethylarginine (SDMA) concentrations are influenced to a lesser extent by muscle mass, and might be a better biomarker of CKD in hyperthyroidism. This study aimed to evaluate serum SDMA concentrations in hyperthyroid cats with and without azotemic CKD.

Hyperthyroid and euthyroid (without azotemic CKD [control]) cats >9 years old were included. Hyperthyroid cats received anti-thyroid medication and were monitored for azotemia (serum creatinine concentration >1.7 mg/dL) during a three month follow up period. Hyperthyroid cats that were azotemic before treatment or during follow up were included in the hyperthyroid-CKD group. Kruskal-Wallis with Dunn ‘s multiple comparisons test was used to compare baseline serum creatinine and SDMA concentrations (SDMA measured by IDEXX Laboratories) between the control, hyperthyroid-CKD and hyperthyroid non-azotemic groups. Median (range) values are presented.

Serum creatinine concentrations in control (1.4 [1.1–1.8] mg/dL, n=8) and hyperthyroid groups were not significantly different, however, serum creatinine was significantly higher in the hyperthyroid-CKD group (1.9 [1.1–2.4] mg/dL, n=5) than the hyperthyroid non-azotemic group (1.1 [0.7–1.3] mg/dL, n=4; p<0.05). Serum SDMA concentrations were not significantly (p>0.05) different between the control (11 [9–13] μg/dL), hyperthyroid-CKD (14 [7–17] μg/dL) and hyperthyroid non-azotemic groups (13 [11–19] μg/dL).

Serum SDMA concentrations did not distinguish hyperthyroid cats with and without azotemic CKD. The influence of hyperthyroidism on serum SDMA concentrations warrants further investigation.