Managing the Hyperthyroid Cat: From Diagnosis to Treatment Options

Hyperthyroid cat getting radioactive Iodine injectionInjection of radioactive iodine, I-131An Explosion of Thyroid Disease Since the 1970’s

Before the 1970’s hyperthyroidism was not a common condition seen in our feline pets. So what’s changed to cause such a dramatic increase in diagnosis? The answer is that we just don’t know. Some suspect that it may be related to the chemicals that we surround ourselves with every day such as the plastics that line the cat food cans or the flame retardant chemicals in our clothes, rugs, and mattresses. As researchers continue to study the possible causes of this endocrine disease, veterinarians and pet owners need to focus on how to diagnose and manage hyperthyroidism successfully.

What is Hyperthyroid Disease?

Hyperthyroidism is a common disease diagnosed in many of our older feline patients (average age at diagnosis is 13 years old). In these patients an excessive amount of the hormone thyroxine, also known as T4, is produced by overactive thyroid glands leading to a variety of symptoms which include:

  • weight loss
  • increased appetite
  • increased activity or restless behavior
  • “crabby” or aggressive behavior
  • increased heart rate
  • GI signs such as vomiting and/or diarrhea
  • increased urination

This excess of the hormone that regulates an animal’s metabolic rate is a result of abnormal growth of thyroid cells referred to as a thyroid adenoma. In most cases theses growths are benign and very responsive to treatment. In 1-2% of cases the abnormal growths are malignant and may involve different treatment options than will be discussed today. Continue…