Are you using thiamazole to treat hyperthyroidism? What dose do you use?
Using this protocol you may be able to predict the dose that your patient should need to control hyperthyroidism
Journal Article
A predictive algorithm for the optimal daily dosage of thiamazole to control cats with hyperthyroidism Open Access
Journal of Veterinary Internal Medicine, Volume 40, Issue 1, January-February 2026, aalag009, https://doi.org/10.1093/jvimsj/aalag009
Published:
03 February 2026
Abstract
Background
Hyperthyroidism is the most common endocrinopathy in cats and is frequently managed using anti-thyroid medication.
Hypothesis/Objectives
To develop and validate an algorithm to predict the optimal starting daily dose of thiamazole required to control hyperthyroidism in cats.
Animals
One hundred eighty-eight client-owned cats with hyperthyroidism for algorithm development (2011-2021) and 45 hyperthyroid cats to validate the algorithm (2022-2024).
Methods
Retrospective case-control study. Cats with hyperthyroidism controlled medically using thiamazole within a year since diagnosis were enrolled. Controlled dose of thiamazole was categorized into “≤5 mg” or “>5 mg.” Binary logistic regression was performed to explore predictors associated with thiamazole dose. The performance of the final multivariable model in prediction was assessed by receiver operating characteristic (ROC) curve analysis. A cohort of cats subsequently diagnosed with hyperthyroidism and managed chronically with thiamazole were used to test algorithm performance.
Results
At hyperthyroidism diagnosis, baseline plasma total thyroxine (TT4); (odds ratio [OR] 1.29 [95% CI, 1.19-1.42] per 10 nmol/L; P < .001) and creatinine concentrations (OR 0.83 [95% CI, 0.7-0.96] per 0.1 mg/dL; P = .02) were independent predictors for higher thiamazole dose (>5 mg). The area under the ROC curve was 0.92 (95% CI, 0.88-0.96). In the test cohort, 26 cats controlled on ≤ 5 mg and 19 required >5 mg thiamazole. The predictive model had overall accuracy of 91.1%, sensitivity of 84.2%, and specificity of 96.2%.
Conclusions and clinical importance
Hyperthyroid cats with higher plasma TT4 and lower creatinine concentrations at diagnosis are likely to require >5 mg total daily dose of thiamazole to achieve euthyroidism.
