Research Communications of the 24th ECVIM-CA Congress

No conflicts of interest reported. Several authors consider thyroid hormone supplementation as a valid initial treatment option for dogs with aggression related problems. Indeed, mood and behaviour modulating properties of thyroid hormones may, in part, be mediated through the interaction of thyroid hormones with neurohormones such as serotonin and prolactin. At present, prospective trials evaluating neurohormonal status or behaviour in hypothyroid dogs before and after thyroid supplementation are lacking. Therefore, the aims of this study were to assess behaviour and measure serum serotonin and prolactin concentrations in dogs with spontaneous hypothyroidism before and after treatment.Twenty three client-owned dogs diagnosed with spontaneous primary hypothyroidism were prospectively included in our study. After diagnosis all dogs were treated with levothyroxine (10 micrograms/kg BID). Behaviour of dogs was screened at initial presentation, at 6 weeks and 6 months after initiation of therapy. Owners had to fill in a hard copy of the standardized Canine Behavioural Assessment and Research Questionnaire (C-BARQ) consisting of 101 scored questions evaluating seven behavioural categories. The average score on all questions was calculated for each dog at each of the three time periods and a paired t-test was used for comparison. Serum serotonin and prolactin concentrations were evaluated at each time period using a commercially validated ELISA kit and heterologous RIA, respectively.Results of the C-BARQ after six weeks of thyroid hormone supplementation when compared with the time zero demonstrated a significant increase (P < 0.05) in excitability, activity and aggression, which most likely became unmasked owing to improved overall activity of dogs. Conversely, at six months period when compared with the time zero no significant changes in any of the behavioural symptoms were observed. Serum serotonin was measured in 18/23 dogs colorimetrically at 450 nm. At time zero, 6 weeks and 6 months serum serotonine was 0.135 (range, 0.075-0.337), 0.141 (range, 0,071-0.392) and 0.149 (range, 0.086-0.378). No significant difference was noted between 6 week and 6 month period comparing to time zero (P = 0.84 and P = 0.37). Serum prolactin concentration measured in 22/23 dogs at time zero, 6 weeks and 6 months was 3.35 ng/ml (range, 1.4-6.36), 3.57 ng/ml (range, 1.87-7.39) and 3.92 ng/ml (range, 2.01-12.92) and did not differ significantly in either time period when compared with time zero (P = 0.99 and P = 0.52).Altogether, results of this study failed to demonstrate a significant role of thyroid supplementation on the majority of evaluated behavioural symptoms as well as neurohormonal status of hypothyroid dogs during 6 months of therapy.