Feline Hyperthyroidism a complete guide

If your adult cat suddenly begins to lose weight despite a voracious appetite, he may have a hormone problem, specifically an overproduction of the hormone produced by the thyroid gland. You should probably bring your feline friend to a veterinarian to be checked for feline hyperthyroidism. Hyperthyroidism is defined as an unregulated overproduction of thyroid hormone from the thyroid gland. This is caused by a benign enlargement or tumour on one or both of the thyroid glands, it is unknown what causes this growth.

The thyroid gland is made up of two butterfly-shaped, flat lobes and is located on either side of the trachea, or windpipe, just below their voice box. The thyroid gland acts as a thermostat for the metabolic rate of the body, controlling how fast or slow the body functions. A surplus of thyroid hormone can affect multiple organ systems.

If you notice any of the following, a visit to your Veterinarian may be needed.

  • Weight loss with normal or increased appetite
  • Vomiting
  • Increased activity or irritability
  • Restlessness
  • Eating non-food items
  • Eating or scrounging for food on countertops, floor, compost bins or out of the sink

Although this disease is usually diagnosed in older cats (at least nine years of age), it has been diagnosed in cats as young as six years of age. There is no recognized breed or sex predilection for this disease.

Your veterinarian will take a detailed history of the signs you’ve been noticing, they will examine your pet to determine if they can palpate (feel) your cats thyroid gland. From there they will collect a blood sample to test for an increased thyroid hormone level and/or take thoracic radiographs (chest/neck x-rays) to try and see an enlarged thyroid gland. Depending on the symptoms your cat is displaying and duration of time they’ve been occurring your doctor may want a more in-depth blood panel as well to ensure normal organ function in the rest of your cat’s body.

Hyperthyroidism is very manageable with medication, Hill’s y/d diet, surgical removal of the affected gland(s) or Radioactive Iodine treatment. With medication, it is typically an oral tablet of Methimazole given twice daily or a transdermal ear gel that you would apply to the inside of your cats ear twice daily. Hill’s pet food has a diet formulated for cats with hyperthyroidism, called y/d. It is specifically formulated with limited iodine, phosphorus and antioxidants to decrease thyroid hormone production; this diet is meant to be fed and used instead of medication. With surgical removal, the doctor will go in and have a look at both glands, remove one or both if enlarged, occasionally when only one gland is removed the other gland may need to be removed in future. Medication is not required after the surgery as removing the affected gland(s) should solve the hyperthyroidism. You can be referred to a specialist vet to have this done if your own doctor doesn’t do the procedure. There is also a Radioactive Iodine treatment in which a doctor treats the gland(s) with radioactive iodine, it destroys the overactive portions of the thyroid gland. This form of treatment has a 95% success rate in cats.

Whichever treatment option you choose needs to be right for you and your cat. If giving medication twice a day seems unrealistic for your day to day schedule then surgical removal or radioactive iodine may be better options for you. Your Veterinarian will be happy to discuss all options and help you make the right decision for your cat.

Written by: Erin Dauphinee, VA/CSS