Hyperthyroidism is caused by an overproduction of thyroid hormone. This condition occurs mostly in older cats and is rare in dogs.

Signs of hyperthyroidism include increased appetite and water intake, weight loss, increased heart rate, vomiting, change in behavior, poor hair coat, and increased urination.

Though enlarged thyroid glands can often be noted during physical examination, hyperthyroidism is diagnosed by bloodwork to check thyroid function.

Treatment options include radioactive iodine treatment, surgery or oral medications, with radioactive iodine being the most recommended treatment option. It is important to discuss with your veterinarian what option is best suited for your pet, as other medical conditions may play a role in what treatment is best.

The prognosis for hyperthyroidism is good for treated patients without other medical conditions.