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Dr. Smith
Dr. Smith, Veterinarian
Category: Cat
Satisfied Customers: 1368
Experience:  Veterinarian in Small Animal Practice for 12 years
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Seizure and Hyperthyroid

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-------------------------------------------------------------------------------- 14 yo cat had a seizure on Tue and Wed mornings. Vet visit Tue show new 2+3+ murmur (since visit 1 year ago), wt loss 13.5 to 10.2. Full senior blood profile came back today (Fri)....hyperthyroid level at 8.2. No seizures since Wed. Question...could the seizures be secondary to organ involvment (cardiac? or other) from the hyperthyroidism? My vet did not think she had heard or seen seizures with hyperthyroid. Trying to get a grasp on if we have two seperate problems or one. I know murmurs and arrythmias can cause clots, but do they usually occur in this scenario? Thanks!!!!!

Hi David,

In a 14 year old cat, hyperthyroidism can be very common. It very commonly does have quite severe side effects on the heart, and most hyperthyroid cats have some degree of cardiomyopathy. Most cases of cardiomyopathy in cats are of the Hypertrophic type which can preclude them to throwing clots. Thromboembolic events or clots can cause various problems in the body ranging from weakness to paralyis to obstruction of cerebral vasculature which could manifest as a stroke or in rare instances possibly induce a seizure.

So to answer your question, hyperthyroidism does not directly cause seizures in the truest sense. Instead, cats with cardiomyopathy secondary to hyperthyroidism can often develop hypertension ( high blood pressure) which can result in vascular accidents or hypoxia( oxygen loss at the tissue level) which may cause seizures.

I would strongly recommend thoracic radiographs, an EKG,and several periodic blood pressure measurements over the course of the day. Your pet should commence treatment of the hyperthyroidism with Methemizole as directed by your veterinarian and I would also consider the usage of Enacard and Baby Aspirin therapy to treat the underlying cardiomyopathy.

Your vet will need to do serial bloodwork testing over the course of Methimazol (Tapazole) treatment in order to insure that the proper maintenance dose is established and that your cat's thyroid levels are back to a normal physiologic level.

Your pet's hyperthyroidism may be due to an actual tumor of one of the thyroid glands ,so surgical removal of the affected gland or radiation therapy may be called for in place of Methamizole therapy.

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Best Wishes to You and Your Pet!
Dr. Jodi L. Smith

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Customer: replied 10 years ago.
Thanks for your insight. My primary vet has me referred to a specialist group here in Atlanta, but the Emergency dept has been the only dept. open since the holiday, so it is hard to wait till Monday to get more insight and I could not find anything on the Internet about seizure activity with hyperthyroidism. I am a CRNA and it is hard to not find/have answers to health problems when you know how to look and understand information...when you can find it! My plan is to go directly to the Radioactive Iodine injection to treat the hyperthyroid and guess I will have to see how the internist wants to work up the cardiac/seizure problem in it's relation or non-relation to that. If you would like, I will let you know the process and outcome next week of the workup.