Changes in biomarkers of redox status in serum and saliva in dogs with hypothyroidism

Abstract Background: Hypothyroidism is the most common endocrine disorder diagnosed in dogs, leading to deleterious effects on dog’s life quality. This study aims to evaluate changes in the redox status in canine hypothyroidism. For this purpose, a comprehensive panel of antioxidants and oxidants was measured in serum and saliva of 23 dogs with hypothyroidism, 20 dogs with non-thyroidal illness and 16 healthy dogs. Among the antioxidants, cupric reducing antioxidant capacity (CUPRAC), ferric reducing ability of plasma or saliva (FRAP or FRAS, respectively), Trolox equivalent antioxidant capacity (TEAC),thiol, paraoxonase type 1 (PON-1) and glutathione peroxidase (GPx) were determined. The oxidant biomarkers included were total oxidant status (TOS), peroxide-activity (POX-Act), reactive oxygen-derived compounds (d-ROMs), advanced oxidation protein products (AOPP) and thiobarbituric acid reactive substances (TBARS). Results: Results showed a significantly higher TEAC, PON-1, GPx, TOS, POX-Act and d-ROMs, and a significantly lower of AOPP in serum of dogs with hypothyroidism, except when AOPP was corrected by serum albumin concentration. Meanwhile, a significantly lower FRAS and AOPP was observed in saliva of dogs with hypothyroidism. Once salivary concentrations were corrected based on their total protein concentrations, the only analyte showing significant changes was TBARS that was significantly higher in dogs with hypothyroidism Conclusions: Our results show thatdogs with hypothyroidism present alterations in the redox status in both serum and saliva. This study should be considered a preliminary study and further research addressing these changes should be made using larger populations.