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Published on: March 29, 2020
Evaluation of hemostasis in hyperthyroid cats
Audrey E Keebaugh1, Stefanie M DeMonaco1, David L Panciera1
1Department of Small Animal Clinical Sciences, Virginia-Maryland College of Veterinary Medicine, Blacksburg, Virginia, USA.
Insights
Hyperthyroid cats show altered hemostasis, with increased fibrinogen and antithrombin levels that normalize after radioactive iodine treatment (RIT). This suggests endothelial dysfunction, not a hypercoagulable state, may contribute to thrombogenesis in these animals.
Area of Science:
- Veterinary Medicine
- Cardiovascular Physiology
- Hematology
Background:
- Hyperthyroid cats may be prone to arterial thrombus formation.
- The underlying mechanism for thrombogenesis in hyperthyroid cats is unknown.
- Systemic hypercoagulability, observed in hyperthyroid humans, is a potential contributing factor.
Purpose of the Study:
- To evaluate hemostasis markers in hyperthyroid cats compared to healthy controls.
- To assess changes in hemostasis markers in hyperthyroid cats before and after radioactive iodine treatment (RIT).
Main Methods:
- Compared hemostatic markers in 25 hyperthyroid cats and 13 healthy euthyroid cats.
- Measured prothrombin time (PT), activated partial thromboplastin time (aPTT), fibrinogen, antithrombin (AT), D-dimers, thrombin-antithrombin complexes (TAT), von Willebrand Factor antigen (vWF:Ag), and factors VIII and IX activity.
- Performed echocardiograms and re-evaluated markers post-RIT in 7 cats.
Main Results:
- Hyperthyroid cats exhibited higher fibrinogen, AT activity, and vWF:Ag compared to controls.
- These markers significantly decreased after RIT.
- No evidence of a hypercoagulable state was found in hyperthyroid cats (P = .08).
- Serum T4 concentration did not predict a hypercoagulable state (P = .53).
Conclusions:
- Hyperthyroid cats demonstrate altered hemostasis, not solely due to cardiac issues.
- A hypercoagulable state was not identified as the cause.
- Altered hemostasis appears to resolve following RIT.
- Elevated vWF:Ag suggests potential endothelial dysfunction, which may promote thrombogenesis.
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 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 : 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 months after successful RIT in 7 cats.
Results:
Hyperthyroid cats had higher fibrinogen concentration (P < .0001), AT activity (P < .0001), and vWF : Ag concentration (P = .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 = .08). Serum T4 concentration was not a predictor of a hypercoagulable state (P = .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 : Ag which could potentiate thrombogenesis.
