Chances are, if you’ve had a few pets in your lifetime you have probably heard about the thyroid gland at least once.  You may have even had a pet or someone you know that required treatment for thyroid problems.

The thyroid is the largest of the endocrine glands.   It is shield shaped and located in the neck near the larynx or voice box.  The thyroid’s job is to secrete hormones which regulate growth and metabolism.  It also acts as a storehouse for iodine.  So when there is a problem with the thyroid gland we will often see significant changes throughout the body systems.

Cats are our most common hyperthyroid patient. We rarely ever see this problem in dogs.  As they age some cats, typically 6 years of age or older, will develop benign nodules on the thyroid which cause over secretion of thyroid hormones.  Hyperthyroidism caused from a cancerous growth is very rare in cats

Signs

When we see hyperthyroid cats in practice our owners will generally tell us that their pet is losing weight in spite of a ravenous appetite. Some cats may also be experiencing vomiting and diarrhea. Many will have concurrent signs of kidney disease and/or failure. Our typical hyperthyroid cat is thin, a bit cranky, a little unkempt and drinking and urinating more than normal.  When we listen to their heart we frequently note a rapid heart rate and possibly a murmur.  A blood pressure check often shows that the cat is hypertensive. If we palpate the pet’s neck we may feel an enlargement of the thyroid gland.

Tests

Laboratory tests are necessary to diagnose hyperthyroidism.  We need to be especially careful to check for any kidney and heart disease as well, since those problems often occur along with thyroid dysfunction.  Blood chemistry and urinalysis will help us detect signs of kidney disease.   Another blood test looks for a high T4 concentration.  Increased levels of this hormone are responsible for most of the troublesome signs we see. There are additional even more sensitive tests that are available if needed.  We may also suggest radiographs (X-Rays) and an ECG if heart disease is a concern

Treatments

Hyperthyroidism is generally treated in one of three ways.

  1. Anti-thyroid drugs:  Methimazole is the most common drug prescribed for hyperthyroidism.  It can be given orally or applied directly to the skin in a transdermal preparation. Methimazole works by decreasing the amount of hormone produced.  It does not cure the underlying disease and must be given for the rest of your cat’s life.  Other drugs may be prescribed if there is concurrent heart disease.

 

  1. Radioiodine therapy is used to destroy thyroid tissue and is considered the gold standard of treatment.  It is safe for the pet but is not as readily available and does require in-patient treatment. However, most universities are able to perform radioiodine treatment.

 

  1. Thyroidectomy or removal of the thyroid gland itself is another effective treatment.  This method requires hospitalization as well.

 

All of the treatments discussed will require some level of follow up.

Hopefully this will aid you in recognizing hyperthyroid problems in your cat earlier should the disease develop.

 Next week we will discuss Hypothyroid disease.