May 15, 2008 "Ask Seth"

My cat Bobby was just tested and diagnosed for feline hyperthyroid at my Pet Assure providing Veterinarian. What is this and how common is it in cats?

Dear Seth,

My cat “Bobby” was just tested and diagnosed for feline hyperthyroid at my Pet Assure Veterinarian.  I am returning early next week for a follow-up with the vet, so I want to know what this disease is and how common is it in cats?  Do I have to treat Bobby?  If so, what is the best for him?




The thyroid is a butterfly shaped endocrine gland that produces hormones called thyroxin (T4) and Triiodothyronine (T3) that regulate metabolism and organ function.  Hyperthyroidism occurs when the thyroid becomes overactive, usually due to the development of a benign tumor (adenoma) in the thyroid gland. Between 2-5% of these tumors are malignant.  Feline hyperthyroidism is one of the most common endocrine conditions affecting cats, usually cats over the age of 10 years old.  Some veterinarians estimate that about 2% of cats over 10 will develop hyperthyroidism.  Due to factors that include environmental exposures that number is on the rise.  For example, researchers report the steady increase of feline hyperthyroidism in the United States may be due to dust from fire-retardant chemicals (PBDEs) used in carpets, furniture, mattresses, electronic products and even pet food. 

Bobby will need treatment.  If this is left untreated, hyperthyroidism can lead to heart failure, kidney failure, and even death.  There are three treatment options for hyperthyroidism.  Each has its pros and cons that need to be discussed with your veterinarian.

1.  Anti thyroid therapy - oral medication twice a day for life.
2.  Surgery.  Thyroidectomy is the removal the affected gland.
3.  Radioactive Iodine.  This injection concentrates in the thyroid and kills the malfunctioning area of the gland.

Speak with your veterinarian about treatment options that are best for Bobby.

Seth Mayersohn, CVT

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