Dr. Mann’s 6-year-old daughter’s
rendering that lead to the naming
of The Cat Company and which
provided the inspiration for the
color scheme of our web site.

What is Feline Hyperthyroidism?

The thyroid is a butterfly shaped gland in your cat’s neck just below the larynx (voice box). This gland is responsible for producing thyroid hormones T3 and T4, which are responsible for maintaining heart rate, breathing, intestinal movement, attitude, sweat glands and overall metabolism. 

Feline hyperthyroidism is a disorder that occurs when the thyroid gland produces too much thyroid hormone. In most cases, about 97% to 98% in fact, the disease is caused by a benign tumor in the thyroid gland that is not responsive to the normal 'on and off' switches that control thyroid function.

 Symptoms of feline hyperthyroidism may include:

  • Weight loss
  • Changes in behavior - anxiety or nervousness
  • Excessive appetite or decreased appetite
  • Increased water intake
  • Hyperactivity or lethargy
  • Excessive shedding, hair loss poor coat condition
  • Diarrhea or vomiting
  • Increased urination
  • Cardiac symptoms - rapid heart rate, arrhythmia

Feline hyperthyroidism is the most common cat endocrine disorder. It occurs most often in middle aged and senior cats. Both sexes and all breeds are at risk. Cats that are not treated may develop thyrotoxic heart disease, a condition similar to hypertrophic cardiomyopathy, where the heart muscle becomes excessively thick. This can lead to heart failure and death.

Why is feline hyperthyroidism so common? The incidence of hyperthyroidism in cats has increased markedly in the last 25 years. We really just don’t know why.  Genetics, immunologic factors, and environmental influences may all be involved.