About Feline Hyperthyroidism

Your one-stop location to learn about this common hormonal disease.


What Is Hyperthyroidism?

Feline hyperthyroidism is a disease caused by an increase in the thyroxine hormone produced by the thyroid gland.  When excess thyroxine is produced, the cat’s metabolic rate soars. The first thing you may notice is excessive eating combined with weight loss.  Please see our symptoms page if you would like some information on other signs to look for. Hyperthyroidism is the most common hormone abnormality found in cats.  Typically, this condition is observed in older cats, with 90% being at least 10 years of age.

What causes hyperthyroidism?

Age is the number one factor, however other determinants can come into play, including:

  • Diet
  • Over functioning thyroid nodules
  • Thyroid cancer, although very rare

What Age/breed is affected?

Hyperthyroidism can occur in any breed, and gender is also not a determining factor. The disease is primarily found in older cats, with 6% of cases linked to cats under the age of 10.