Maggie the Cat and Feline Hyperthyroidism

Maggie is a 15 year old Tabby belonging to Dorothy Swenson and family. She was brought in to see Dr. Schaeffer last month for weight loss, more frequent vomiting, and vocalizing more around the house. Her vocalizing was mainly at night and seemed to be somewhat random. Maggie’s owners had also observed that she was pulling her fur out in several places.

On exam, Maggie was noted to have a thin body condition and hair coat. Her thyroid glands were slightly enlarged when palpated and her heart rate was faster than normal, at 250-300 beats per minute (tachycardia). Blood and urine samples were collected and showed that Maggie had an elevated thyroid hormone level, caused by feline hyperthyroidism.

Hyperthyroidism is a common endocrine disease seen in older cats. As you might suspect by its name, the thyroid glands make more thyroid hormone than normal. Most of the time, this is caused by a benign tumor growing on one of the glands.

Symptoms of an abnormally high thyroid hormone level in cats include:

• High heart rate
• Weight loss despite a good appetite
• Vomiting and diarrhea in many cases
• Some affected cats will groom their hair coats in an anxious way, similar to Maggie.
• Heart disease and high blood pressure can also result from hyperthyroidism

There are two commonly recommended treatments for hyperthyroid cats, and both were discussed with Maggie’s owners:

Methimazole
The first is an oral medication called methimazole that must be given once or twice daily. It blocks the production of thyroid hormone and, given at the right dose, the thyroid hormone can be kept within normal range. Repeated bloodwork is needed to monitor thyroid levels, and oral medication is continued long term.

Radiotherapy
The other option for feline hyperthyroidism is radiotherapy, offered at special hyperthyroid treatment centers in the area. A radioactive iodine injection is administered after a nuclear medicine scan is performed. The advantage to this treatment modality is that no further treatment is typically required.

Both treatment options require follow-up bloodwork to monitor not only thyroid levels, but kidney values, as treatment of hyperthyroidism can uncover underlying kidney disease. Maggie’s owners chose to start methimazole and will be rechecking her bloodwork soon. Hopefully she is already starting to feel better!