2015 ACVIM Forum Research Abstract Program

Serum concentrations of T4, thyroid stimulating hormone [TSH], and creatinine were assessed at 0, 3, and 6 months after treatment. Cats were categorized at each time interval as having persistent hyperthyroidism, euthyroidism (normal T4 [0.9-4.0 lg/ dL] and TSH [≤ 0.3 ng/mL]), overt hypothyroidism (low T4, high TSH), or subclinical hypothyroidism (normal T4 but high TSH) (Table) . Categorical and continuous data were analysed using Chi-Square and Wilcoxon Rank Sum, respectively, with P < 0.05 considered significant. At baseline, there were no differences in sex, age, or serum concentrations of T4, TSH, or creatinine between treatment groups. Cats treated with 2 mCi 131 I were significantly (P ≤ 0.01) less likely to develop overt hypothyroidism at 3 and 6 months compared to cats treated with 4 mCi. There was no significant difference in persistent hyperthyroidism between groups. Cats dosed with 4 mCi 131 I had significantly (P ≤ 0.007) higher median creatinine concentrations at 3 (1.9 mg/dL) and 6 months (2.0 mg/dL) than did cats receiving 2 mCi (1.6 mg/dL and 1.7 mg/dL, respectively).