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.