Hyperthyroidism

An overactive thyroid is the most common endocrine disorder in cats. This is generally not due to a tumor and is very treatable. If the condition is left untreated, the patient will develop body-wide organ dysfunction.

In almost all cases, the thyroid nodules simply start making more thyroid hormones. It is very rarely due to a malignant mass on the thyroid gland.

Cats with hyperthyroidism will eat voraciously but still lose weight, vomit, have diarrhea, drink and urinate more. Many patients become aggressive toward owners and are restless. Some will have a murmur on physical exam and an enlarged thyroid may be palpated.

The best treatment is radiation of the thyroid gland. This is actually a very simple procedure where the patient is given an injection of radioactive iodine. The only downside is the patient must stay at the veterinary facility until their level of radiation has decreased. This can take several weeks. Any further treatment needed after radiation is rare.There is also an oral medication that blocks the production of thyroid hormones. Tapazole is a very commonly used drug and must be given twice daily. For cats that are hard to medicate, a gel that is rubbed onto the surface of the pet’s ear can be prescribed. Oral medication only controls the disease and does not cure it. All cats will need routine blood work to check thyroid function and medication adjustments are common. Most cats will begin to become somewhat resistant to Tapazole and it may stop being effective. This is usually observed approximately 2 years after initiation of treatment.