Hyperthyroidism and the Importance of Lab Work

Hyperthyroidism and the Importance of Lab Work

As they age, a cat’s risk for disease increases. Regular veterinary visits help reveal and remedy concerns regarding your feline friend’s health and well-being. Hyperthyroidism is an excellent example of a highly treatable and diagnosable condition that our staff regularly encounters at Nob Hill Cat Clinic and Hospital.

What is Hyperthyroidism?

Hyperthyroidism, also known as thyrotoxicosis, is a result of an increase in production of T3 and T4 thyroid hormones and is caused by an enlarged thyroid gland. A cat’s thyroid gland is located in their neck and impacts almost every organ in their body. The root cause of feline hyperthyroidism is not known, but treatment is generally very effective.

A cat with hyperthyroidism will often appear disheveled, thin, and present with increased appetite and thirst. Owners may notice that their cat is losing weight in spite of their insatiability. Other symptoms may include: vomiting, diarrhea, irritability, hyperactivity, vocalization, and occasional weakness, depression, or trouble breathing. Please keep in mind that every cat is unique and may or may not experience specific symptoms.

The best way to ensure your feline friend remains happy and healthy is to schedule regular veterinary check-ups and lab work when recommended.

Why is My Vet Recommending Bloodwork for my Senior Cat?

Regular bloodwork and urinalysis for senior cats is a crucial aspect of preventative care, as hyperthyroidism is much more common in older cats. In fact, only 5% of cats suffering from hyperthyroidism are under 10 years of age. Bloodwork reveals whether or not your cat has elevated levels of T4 in their bloodstream, allowing your vet to catch or confirm the condition.

An early diagnosis and subsequent treatment can help stabilize your cat and prevent complications, including heart disease and high blood pressure. Complications resulting from hyperthyroidism can have a detrimental effect on your cat’s eyes, heart, brain, and kidneys. A full lab panel illuminates your cat’s overall condition, the first step for successful treatment of disease and a healthy lifestyle.


How is Hyperthyroidism Treated?

There are three major forms of treatment for hyperthyroidism. An exam and lab work can help your veterinarian determine the best course of action for you and your pet. No treatment is ‘one size fits all,’ as factors such as your cat’s overall health and financial flexibility may come into play.


Medication is a typical, effective method of treating hyperthyroidism and is often a good choice for cats with resulting complications. Methimazole, also known as Tapazole, is relatively  inexpensive and is administered daily for the rest of a cat’s life. Tapazole works by lowering your pet’s thyroid hormone levels. If discontinued, these levels will begin to rise again.

Your veterinarian will most likely want to continue to monitor your cat’s T4 levels via regular blood work. Tapazole, like many medications, has possible side effects including: vomiting, depression, and reduction in appetite. These symptoms often resolve without discontinuing medication. Some cats may develop low blood cell counts, making consistent bloodwork especially critical in monitoring a cat’s progress.

Tapazole is an excellent option for pet parents that are able to effectively administer medication, have a cat with a comorbid condition, or are looking for a budget-friendly solution.

Radioactive Iodine Therapy

Radioactive iodine therapy is extremely effective in most cases and involves an injection of radioactive iodine which is absorbed into a cat’s bloodstream. It eliminates abnormal thyroid tissue while leaving healthy, normal tissue intact. This form of treatment is fast-acting, low-risk, and generally expensive.

Radioactive iodine therapy must be administered at a specialized facility, and, unfortunately, there are few in California. After treatment, cats are kept at the facility for several days until radiation levels reduce to an acceptable level. Most cats need no further hyperthyroid treatment post-therapy. In rare cases, a pet may develop hypothyroidism as a result of treatment.

Surgical Removal of the Thyroid Glands

Cats generally need to be otherwise healthy in order for surgical removal of the thyroid glands to be a viable option. This treatment is generally successful in treating hyperthyroidism. However, any surgery carries risk; in addition to complications as a result of anesthesia, damage to surrounding tissue may occur.

Due to the effectiveness of other therapies as well as potential risks involved in surgery, removal of the thyroid glands is not usually recommended.  


Ultimately, your cat’s health and safety is always our clinic’s priority. Our veterinary staff will work with you to develop the most effective, feasible treatment plan for your unique feline friend.

By Kaitlin Murphy