Hyperthyroidism leads to a decrease in serum creatinine (Crea) by increasing glomerular filtration rate (GFR) and decreasing body muscle mass. This can mask a concurrent chronic kidney disease that might become evident after the onset of treatment. Symmetric dimethylarginine (SDMA) is a novel, early, renal biomarker independent of body muscle mass, therefore it might be a useful marker of renal disease in hyperthyroid cats. In humans is not clear if hyperthyroid state could influence SDMA.

Aim of this study was to evaluate SDMA in hyperthyroid cats at the time of diagnosis and after treatment.

This was a retrospective observational study. Nineteen hyperthyroid cats (TT4>40 mmol/L) with normal Crea (<1.8 mg/dl) were included. Eighteen healthy cats, older than 7 years, with normal TT4 and Crea <1.8 mg/dl were enrolled as control group. Data about physical exam, emogram, serum biochemistry and serum TT4 concentration were evaluated. SDMA was measured on serum left over from previous analyses and stored at -80°C. SDMA measurement was performed in serum samples collected at the time of diagnosis of hyperthyroidism and after methimazole treatment when TT4 normalized, between 10 to 90 days after initiation of the treatment. Follow-up was available for 8/19 hyperthyroid cats; SDMA was measured using a validated immunoassay (IDEXX SDMA test).

Hyperthyroid cats were older (p=0.0005) and had a lower weight (p<0.0001) than control cats. In hyperthyroid cats Crea at diagnosis was positively correlated with SDMA (r=0.47, p=0.04) and negatively correlated with TT4 (r=-0.46, p=0.04). No correlation was found between SDMA and TT4 at diagnosis (p=0.10). In hyperthyroid cats weight was positively correlated with creatinine (r=0.51, p=0.004) but not with SDMA (p=0.39). There was no difference for Crea between hyperthyroid cats and controls at diagnosis (p=0.3). Creatinine significantly increased (p=0.03) after treatment despite body weight did not (p=0.13). No difference was found when comparing SDMA in hyperthyroid and control cats at diagnosis (p=0.11) nor after treatment (p=0.86). Five hyperthyroid cats had SDMA value higher than reference range at diagnosis. Follow-up after treatment was available for 2/5 only; in these 2 cats when TT4 was normal Crea was still normal and SDMA was increased in one. 2/5 cats showed increased creatinine when TT4 normalized, but none of them had high SDMA at diagnosis.

Based on this preliminary study hyperthyroidism seems not to influence SDMA concentration.

Disclosures

No disclosures to report.