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The thyroid gland produces essential hormones that are involved in the regulation of many vital body functions. Tumors of the thyroid gland can cause over production of these hormones, or hyperthyroidism. Hyperthyroidism usually develops gradually and can be difficult to notice in the early stages.

In cats, the thyroid tumors are usually benign and do not spread to other organs. In dogs, thyroid tumors have much more potential to be malignant and spread throughout the body.

Pets may exhibit one or many of these common signs including:

  • weight loss
  • increased appetite (can increase greatly)
  • increased water intake
  • frequent stools
  • restlessness
  • crying
  • panting

Diagnosis is based on clinical signs, examination findings and blood work that includes testing the level of thyroid hormone present. Treatment varies depending on tumor type, species, and stage of disease.

Common treatments for feline hyperthyroidism include:

  • Administration of a drug
  • Irradiation (radiation treatment) of thyroid tumor tissue.
  • Surgical removal of the thyroid tumor tissue.

For canine hyperthyroidism, surgical removal of the thyroid tumor is usually recommended, as these tumors have much more potential to be malignant. Dogs may receive medication or radiation treatment as well.


  • Use all medications as prescribed by your veterinarian.
  • Your pet will need thyroid hormone level checks and other blood tests as directed by your veterinarian.
  • Monitor your pet's progress carefully and have him or her rechecked if you have any concerns.

If you have questions about this or any medical topic, please contact your Banfield hospital today.