Evaluation of hemostasis in hyperthyroid cats.

Abstract

BACKGROUND: Hyperthyroid cats might have a predisposition to arterial thrombus formation. The mechanism for thrombogenesis currently is unknown but could be associated with systemic hypercoagulability as seen in hyperthyroid humans. OBJECTIVE: Our purpose was to evaluate markers of hemostasis in hyperthyroid cats compared to healthy cats, and in hyperthyroid cats before and after radioactive iodine treatment (RIT). ANIMALS: Twenty-five cats with hyperthyroidism and 13 healthy euthyroid cats >8&#x2009;years of age. METHODS: Prothrombin time (PT), activated partial thromboplastin time (aPTT), fibrinogen concentration, antithrombin (AT), D-dimers, thrombin-antithrombin complexes (TAT), von Willebrand Factor antigen (vWF&#xa0;:&#xa0;Ag), and activity of factors VIII and IX were measured. An echocardiogram was performed in all cats. Hemostatic markers and echocardiogram were evaluated again 6 to 9&#xa0;months after successful RIT in 7 cats. RESULTS: Hyperthyroid cats had higher fibrinogen concentration (P&#xa0;<&#x2009;.0001), AT activity (P&#xa0;<&#x2009;.0001), and vWF&#xa0;:&#xa0;Ag concentration (P&#xa0;=&#x2009;.01) than healthy control cats with all results decreasing significantly post-RIT. Hyperthyroid cats were not more likely to be in a hypercoaguable state than euthyroid cats (P&#xa0;=&#x2009;.08). Serum T4 concentration was not a predictor of a hypercoagulable state (P&#xa0;=&#x2009;.53). CONCLUSIONS AND CLINICAL IMPORTANCE: Hyperthyroid cats have evidence of altered hemostasis that does not appear to be solely attributable to cardiac abnormalities, but no evidence of a hypercoagulable state. Findings suggest altered hemostasis resolves after RIT. Hyperthyroid cats could have endothelial dysfunction as indicated by increased vWF&#xa0;:&#xa0;Ag which could potentiate thrombogenesis.