Mrs. Dodson showed up with circles under her eyes for her cat’s annual exam – she was clearly tired. As the cat carrier’s door jostled I heard Tipper yowl and suspected why Mrs. Dodson might be losing sleep.
During my physical exam I noted that Tipper lost a pound and a half, had an elevated heart rate, and I could feel a small nodule on his throat. I recommended that we conduct blood work and a urinalysis to assess his thyroid levels, monitor his kidney and liver function, and screen for any other abnormalities.
The next day, the lab confirmed our suspicions. Tipper was hyperthyroid. In addition to high levels of thyroid hormones, Tipper also had borderline abnormalities in some of his laboratory results that suggested early kidney disease.
Hyperthyroidism, or the overproduction of thyroid hormones, is the most common endocrine disease affecting cats over 8 years old. Because thyroid hormones play such an important role in metabolism, hyperthyroidism has far-reaching effects. The classic signs of hyperthyroidism are weight loss, increased appetite, and restlessness. We may see changes in coat condition and grooming behavior, increased drinking and urinating, vomiting or diarrhea. Paradoxically, some cats can become weak and tired, or even lose their appetite. Sometimes, as in Tipper’s case, your veterinarian will be able to feel a small mass on the cat’s throat or will note an increased heart rate or abnormal heart rhythm or murmur.
Hyperthyroidism can have negative effects on the heart. Depending on which secondary cardiac problem develops, these changes may be reversed by treating the thyroid disease. Another complication is that many older cats also have kidney disease. Though the two are not always directly related, in some cases, hyperthyroidism can mask kidney disease. Successful management of these two diseases concurrently can be challenging, but is achievable.
Long-term treatment options for hyperthyroid disease include daily medications, surgical removal of affected thyroid gland(s) and treatment with a radioactive form of iodine that targets and destroys active thyroid cells. A special kind of scan, called a radionuclide thyroid scan, is often performed before either of the more permanent treatments to help the veterinarian decide upon the best treatment plan and predict the likelihood of success and risk of complications.
Tipper’s thyroid hormone levels were regulated on oral anti-thyroid medications, and his symptoms disappeared. Fortunately, his kidney values remained stable and Mrs. Dodson then opted for the more permanent radioactive iodine treatment. Tipper, now back to his normal self, takes no medications, no longer wakes Mrs. Dodson, and needs only occasional blood work to monitor his condition.
The case described here is based on a true story, but details about the patients and clients have been altered to protect their privacy. Most importantly, this story is not meant to convey instructions for treating or diagnosing your pet – please see your veterinarian if you have any health-related suspicions of your pet.