Canine hypothyroidism is associated with decreased glomerular filtration rate (GFR), while serum creatinine (SCr) concentrations are rarely increased above the reference interval (RI) in hypothyroid dogs. Symmetric dimethylarginine (SDMA) is considered a biomarker for early detection of renal dysfunction and resulted strongly correlated with GFR in dogs. In humans, SDMA is significantly higher in hypothyroid compared to healthy people. The aim of this study was to evaluate the SDMA concentrations in a population of hypothyroid dogs (HD) at the time of diagnosis (T0) and after treatment (T1). Fourteen dogs affected by spontaneous hypothyroidism and 20 healthy dogs (control group) were included. The diagnosis of hypothyroidism was based on consistent clinical signs, laboratory findings, including serum total T4 and cTSH concentrations below and above the RI, respectively. In dogs with normal cTSH, rhTSH stimulation test was performed to confirm the diagnosis. SCr was measured for diagnostic or check-up purposes and SDMA was measured afterwards from surplus of serum stored at -20°C. In HD such measurements where performed at T0 an after 15 to 112 days (median 64.5) of treatment (T1) with levothyroxine (10–15 µg/kg q12h PO). SDMA was measured using a validated immunoassay (IDEXX SDMA test). HD had a median age of 4 years (4–15), median body weight (BW) of 37.5 kg (7.9–53), 7/14 were male (1 castrated) and 7/14 female (3 spayed). There were no significant differences regarding signalment and BW between HD and control group. Median SDMA concentrations (RI<14 µg/dl) were 10 µg/dl (6–17), 13.5 µg/dl (7–20) and 10.5 µg/dl (5–17) in healthy dogs, HD at T0 and T1, respectively. SDMA concentrations were significantly higher in HD at T0 in comparison with healthy dogs (p<0.029) and HD at T1 (p<0.031). Among HD, 7/14 had SDMA above the RI at T0 and only 1/14 (7%) at T1. At T0, 4/14 HD had SCr above the RI (>1.35 mg/dl). SCr concentration was significantly higher in HD at T0 compared to HD at T1 (p<0.0082), and in one dog SCr was above the RI at T1. No significant correlation was observed between SDMA and T4, and SDMA and SCr in the HD at T0 and T1.

This study shows that in HD SDMA concentrations are frequently above the RI at diagnosis and normalize after treatment. The GFR modifications that are present in canine hypothyroidism may be better detected with SDMA compared to SCr.

Disclosures

No disclosures to report.