Hyperthyroidism is a common condition in cats and is caused by an overproduction of thyroid hormone due to a tumor in the thyroid glands. These hormones are important for regulating various bodily processes. Overproduction can lead to several health problems. The Academic Veterinary Hospital in Utrecht specializes in diagnosing and treating thyroid problems (hyperthyroidism) in cats. On this page, you will find more information about the symptoms, diagnosis, and various treatment options. 

Symptoms of hyperthyroidism in cats

Cats with hyperthyroidism can exhibit a variety of symptoms, including:

• Weight loss (emaciation), often despite a good appetite 
• Hyperactivity 
• Increased drinking and urination 

This condition is usually seen in cats from the age of 8 years, but can also occur in younger cats. Since thyroid tumors in cats are often benign, treatment is generally possible.

Associated health problems

In addition to the above symptoms of hyperthyroidism, the condition can lead to other health problems, such as heart issues. Thyroid hormone also affects kidney function. Timely diagnosis and starting a proper treatment as soon as possible are therefore important.

Diagnosis of hyperthyroidism

To diagnose hyperthyroidism, doctors can use blood tests and a thyroid scan (scintigraphy). 

Blood test

Blood tests in cats can help diagnose hyperthyroidism and identify other health problems that your cat may have. The cost of a blood test for your cat can vary greatly and depends on the condition of your cat. Contact your veterinarian for more information.

Thyroid scintigraphy

Scintigraphy (thyroid scan) is a specialized diagnostic technique used to image the thyroid glands. During this test, a small amount of radioactive substance, similar to iodine, is administered into the bloodstream. This substance has the unique property of concentrating in active thyroid tissue, allowing for a detailed image of the shape, size, and function of the thyroid glands.

The Academic Veterinary Hospital in Utrecht has the necessary permits to use radioactive substances and is one of the few facilities in the Netherlands authorized to perform these diagnostic scans.

Thyroid cat treatment

There are various options for treating hyperthyroidism in cats:

• Medication (thyroid suppressants) 
• Special (diet) food 
• Administration of radioactive iodine 
• Surgical removal of thyroid tumor tissue

Each of these treatment options has certain advantages but may also have disadvantages. The choice of treatment method depends on the specific situation of the cat, the severity of the condition, and the preferences of the owner.

Thyroid medication for cats

There are several medications that can inhibit the production of thyroid hormone, including methimazole, strumazole, and carbimazole. The cat must take this medication for the rest of its life. The medication does not inhibit tumor growth. These medications can have side effects, such as poor appetite, vomiting, liver problems, bone marrow issues, and skin problems. 

Thyroid cat food

Feeding special (diet) food with low iodine can reduce the production of thyroid hormone. A major advantage of this approach is that the use of medication may become unnecessary. An important disadvantage is that the cat must not eat any other food, including cat treats. Additionally, not all cats like this food. 

Surgical removal of thyroid tumor tissue

Surgical removal of thyroid tumor tissue is particularly suitable if the condition is limited to one of the two thyroid glands. In 70% of cats with hyperthyroidism, both thyroid glands are affected, and there are risks associated with the surgical removal of thyroid tumor tissue.

Radioactive Iodine

Treatment with radioactive iodine is a highly effective method. A single administration of radioactive iodine usually leads to a definitive cure. This radioactive iodine is absorbed by the tumor cells in the thyroid glands, destroying these cells without noticeable effects on the healthy tissues of the body.

Contact and questions

For more information or to make an appointment, please fill out our “contact form for thyroid issues in cats” (in Dutch). Our case managers will then contact you.