The aims of this study were estimation of thyroxin status in dogs infected with B. canis, and determination of the association between azotaemia and concentrations of total thyroxin (TT4) and free thyroxin (FT4) in canine babesiosis. Concentrations of TT4 and FT4 were determined using an immunoassay in 23 dogs infected with B. canis (nine azotaemic dogs and 14 non-azotaemic dogs). Mann-Whitney U test was used to compare the concentrations of TT4 and FT4 in groups of azotaemic and non-azotaemic dogs. Correlations between azotaemic parameters (i.e. serum urea and creatinine) and TT4 and FT4 concentrations were calculated. The obtained results showed high prevalence of dogs infected with B. canis showing decreased TT4 and FT4 concentrations. No difference between concentrations of TT4 and FT4 in azotaemic and non-azotaemic dogs was demonstrated, but statistically significant correlations between the level of TT4 and FT4 and serum levels of urea and creatinine were shown.
