Jan 01 2012


Hyperthyroidism and Renal Insufficiency

Just over 2 years ago Scooby was found as a stray by the Hendricks family. He was very skinny, had a tremendous appetite but seemed to be otherwise healthy. Scooby couldn’t have made a better choice, and settled in with his new family.

Late this summer it seemed Scooby was losing weight. Despite being bright, active and eating more than his share, he just seemed to be shrinking away. It was time to have Scooby examined, so he was brought to Riverside Small Animal Hospital.

On examination Scooby was very lean weighing only 3kg when he should have been nearer to 5kg. Scooby had a significantly elevated heart rate, small feeling kidneys and generally poor muscle tone. Palpation of his neck suggested a possibly enlarged thyroid gland (the thyroid is not normally evident in cats). A senior blood health screen including a complete blood count, serum biochemistry, thyroxine (T-4, thyroid hormone) and urinalysis was performed. Based on these tests it was determined that Scooby had hyperthyroidism and renal insufficiency.

Hyperthyroidism is a common disorder that occurs in cats, it is caused by hyperfunctioning nodules that develop in the thryroid gland and release abnormal amounts of T-4 into circulation. It typically occurs in cats over 8 years of age. Hyperthyroidism affects multiple body systems including the heart, intestinal tract, the kidneys, the nervous system and behavior. Fortunately management of hyperthyroidism is available and generally successful in reducing severity or alleviating many of the secondary effects of elevated T-4. The goal is to reduce the amount of T-4 being released into circulation. Given Scooby’s good nature and dedicated owners, it was decided to place Scooby on oral Methimazole. Methimazole is a medication that selectively controls the abnormal production of T-4.

Soon after methimazole therapy commenced; Scooby’s owners noted that he was scratching face and ears more than he ever had before. Facial itchiness, is a know symptom of methimazole hypersensitivity (allergy). If this symptom develops there is no other oral medication which can be used to successfully manage hyperthyroidism. Once Scooby was taken off the methimazole his itchiness resolved, confirming the allergic response.

With this treatment complication there were only two other ways of addressing Scooby’s hyperthyroidism. One being radioactive Iodine treatment which meant a trip with Scooby to Vancouver for treatment.  Then following treatment a number of days where the cat is kept in isolation (because they are temporarily radioactive) until it can safely return home. The other procedure is surgical removal of the thyroid glands (thyroidectomy), a more invasive procedure and there can be local damage to associated structures such as the parathyroid glands or local nerves.

After weighing their options, Scooby’s owners chose thyroidectomy and on November 22, 2011 Scooby had both of his thyroid glands removed. When conducted by an experienced surgeon the surgical risks are very small, and follow-up examination and blood work confirmed that the parathyroid glands are functioning and there was no significant damage to local nerves. Scooby has recovered well from the procedure, doesn’t require daily medications and will be monitored for any changes including return of symptoms or weakness. Although Scooby still has to deal with his reduced renal function, close management of his diet should help him live a long and happy life!

LifeLearn Admin | Pet Of The Month