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Feline Hyperthyroid Treatment Clinic

 Dr. Karyn Harrell
 Dr. Katharine Lunn

Contact Information

Phone: 919.513.6670
Fax:     919.513.6713
Hours:   Monday-Friday, 8AM-5PM

Veterinary Health and Wellness Center

red Cross Cadeceus

Emergency Service

Main Number: 919.513.6500
Small Animal Emergency: 919.513.6911
Large Animal Emergency: 919.513.6630
Monday-Thursday 5PM-8AM
Friday 5PM-Monday 8AM

Open 24 hours on legal holidays.
No appointment needed.

Feline Hyperthyroid Treatment Clinic

black cat

Hyperthyroidism is caused by a thyroid tumor (usually non-malignant) and is currently the most common endocrine disease in older cats.  Clinical signs are progressive and can be severely debilitating and potentially fatal if the disease is left untreated.

Common Symptoms

Overproduction of thyroid hormone causes an increase in a cat’s metabolic rate and can result in any of the following symptoms:

Owners should consult their primary veterinarian for an initial assessment of their pet.  A physical examination and diagnostic testing consisting of routine blood work, urinalysis and a thyroid level will be conducted to determine the overall health of the cat.  Occasionally, further testing may be needed but the results of this initial assessment are often sufficient to diagnose hyperthyroidism and determine if the cat is a candidate for radioactive iodine treatment.


The current treatment of choice is destruction of the abnormal thyroid tissue with radioactive iodine (I131).  A specific dose of radioactive iodine is administered by a single injection under the skin.  (This is the same basic procedure as giving a vaccine.)   The cat will then stay in the hospital for approximately 4 days so we can adequately monitor radiation levels.  This single injection will cure 95% of cats with no need of further treatment for this disease.  In addition to being safe and very effective, over time it is also likely to be the least costly and stressful way to treat hyperthyroidism.

catMedical therapy acts by inhibiting thyroid hormone synthesis with drugs such as Methimazole.  While these drugs are able to control symptoms of the thyroid tumor, they are not curative.  Over-secretion of thyroid hormones will return if therapy is discontinued which means that twice daily medications are needed for the life of the cat.  In addition, these medications occasionally have undesired side effects.

Surgical excision of the affected tissue is curative as long as additional overactive thyroid tissue has not migrated to other areas.  As with any surgery, both anesthetic and surgical complications can occur and this form of treatment is currently not considered optimal.



Each cat will stay in our luxurious cat cottages with a faux sheepskin bed, cardboard scratching post and lots of toys.  Our caring staff will make sure all of the cats receive lots of love and attention during their stay.

Post Treatment Care

Each cat will stay in the hospital for 4 days for monitoring of radiation levels, with a recheck at 30 days post discharge, 60 days post discharge and then annually thereafter.  Certain precautions will need to be taken with litter disposal and contact for 7 days after bringing the cat home.   We will go over these details and recommendations for follow up care at the time of discharge.