Categories: Cat Health

Feline Hyperthyroidism

by Michael
(London, UK)

Feline hyperthyroidism is a disease caused by the excessive production of the hormone, thyroid (thyroxin) by the thyroid gland. This gland is in the neck3.

The term “hyper” in medical parlance means: high, beyond, excessive, above normal 2.

The term “ism” means: condition of, practice of, theory of1.

Feline hyperthyroidism is the most common feline hormone disorder.

The thyroid gland enlarges causing a swelling in the neck.

The symptoms:

  • Restlessness
  • Irritable
  • Pace up and down
  • Excessive hunger
  • Excessive food consumption
  • Weight loss
  • Vomiting
  • Increased volume of faeces
  • Hair loss and hair pulls out easily

The heart works harder. It can lead to a “form of cardiomyopathy”, which in turn leads to congestive heart failure.

Other illnesses associated with old cats can mask hyperthyroidism in cats.


Please see a good vet. Blood test are required.


Objective: return thyroid production to normal. Methods:

  • Drugs
  • Removal of the thyroid gland
  • Administering radioactive iodine at a specialist clinic

Associated Page:

The opposite is feline Hypothyroidism.


1. 2.


3. Cat Owner’s Home Veterinary Handbook page 385 – 386, by Drs Carlson and Giffin.

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Michael Broad

Hi, I'm a 71-year-old retired solicitor (attorney in the US). Before qualifying I worked in many jobs including professional photography. I have a girlfriend, Michelle. I love nature, cats and all animals. I am concerned about their welfare.

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