Find Information About:

Drugs & Supplements

Get information and reviews on prescription drugs, over-the-counter medications, vitamins, and supplements. Search by name or medical condition.

Pill Identifier

Pill Identifier

Having trouble identifying your pills?

Enter the shape, color, or imprint of your prescription or OTC drug. Our pill identification tool will display pictures that you can compare to your pill.

Get Started

My Medicine

Save your medicine, check interactions, sign up for FDA alerts, create family profiles and more.

Get Started

WebMD Health Experts and Community

Talk to health experts and other people like you in WebMD's Communities. It's a safe forum where you can create or participate in support groups and discussions about health topics that interest you.

  • Second Opinion

    Second Opinion

    Read expert perspectives on popular health topics.

  • Community


    Connect with people like you, and get expert guidance on living a healthy life.

Got a health question? Get answers provided by leading organizations, doctors, and experts.

Get Answers

Sign up to receive WebMD's award-winning content delivered to your inbox.

Sign Up

Healthy Cats

Select An Article

Hyperthyroidism in Cats

Font Size

How Is Hyperthyroidism Treated?

Several treatment options for hyperthyroidism exist, each with advantages and disadvantages.

  • Oral administration of antithyroid medication. Methimazole (brand name TapazoleTM) has long been the mainstay of drug therapy for feline hyperthyroidism. It is highly effective in correcting the condition, often within two to three weeks. Unfortunately, about 10%-15% of cats will suffer side effects, such as loss of appetite, vomiting, lethargy, and occasionally blood cell abnormalities. Rare but more serious side effects include severe facial itching with self-induced trauma, blood clotting disorders, or liver problems. Most side effects are mild and eventually resolve, although some necessitate discontinuation of the medication. Lifelong daily medication is required, which is a disadvantage to owners whose cats resist pilling. CBC and T4 levels need to be rechecked regularly for the remainder of the cat’s life.
  • Surgical removal of the thyroid gland. Hyperthyroidism is usually caused by a benign tumorcalled a thyroid adenoma that involves one or, more often, both thyroid glands. Fortunately, most hyperthyroid cats have benign, well-encapsulated tumors that are easily removed. Surgery usually results in a palliation and not a cure, but anesthesia can be challenging in these older patients whose disease may have affected their hearts and other organs. Although surgery may seem costly, it often ends up being less expensive than years of oral medication and regular bloodwork rechecks.
  • Radioactive iodine therapy. This is probably the safest and most effective treatment option. Radioactive iodine, given by injection, becomes concentrated in the thyroid gland, where it irradiates and destroys the hyperfunctioning tissue. No anesthesia or surgery is required, and only one treatment is usually needed to achieve a cure. It used to be that radioiodine treatment was performed only in specialized, licensed facilities, but many private treatment facilities are now found throughout the country. Hospitalization may be prolonged; depending on local or state ordinances, cats may need to be kept at the treatment facility for 10 to 14 days until the level of radioactivity in their urine and feces decreases to an acceptable level. Also, radioiodine therapy is costly. The price tag has come down from about $1,200 to between $500 and $800-but this is still prohibitive for many cat owners.

This information was adapted from an article written by Arnold Plotnick, DVM.

WebMD Veterinary Reference from the ASPCA

Next Article:

Today on WebMD

cat at table
What's safe for them to eat?
Maine Coon cat breed
What they do and why cats have them.
Kitten in litterbox
How to solve them.
cat meowing
Why some cats are so talkative
cat on couch
Kitten using litter box
sleeping kitten
sad kitten looking at milk glass
cat at table
muddy dog on white sofa
Maine Coon cat breed
Pets: Behavior Problems in Cats