Comparison of survival times of cats with hyperthyroidism treated with thyroidectomy or methimazole at a primary care hospital in Japan

OBJECTIVE We identified the associated factors and compared the survival times of feline hyperthyroidism (FHT) between thyroidectomy and methimazole alone. METHODS The medical records of 41 cats diagnosed with new-onset hyperthyroidism were retrospectively reviewed. The cats were categorized into the thyroidectomy (n = 15) and methimazole (26) treatment groups. Survival analyses using the Kaplan-Meier method, log-rank test, and Cox proportional hazards models were conducted to compare the time to the selected outcomes. RESULTS Univariate analysis revealed that survival time was significantly longer with thyroidectomy than with methimazole ( P < .001). Multivariate analyses revealed thyroidectomy as an independent prognostic factor for good outcomes (hazard ratio, 0.209; 95% CI, 0.073 to 0.601; P = .004). The recurrence rate was significantly lower in cats that underwent thyroidectomy than in those that received methimazole alone ( P = .011). CLINICAL RELEVANCE Compared with methimazole alone, thyroidectomy was associated with a longer survival time in FHT and can be considered an irreversible treatment modality in settings where radioisotopes are not available.