Recognizing Cat Hyperthyroidism Symptoms in Senior Cats

In many ways, cats just seem to get better with age. While there is nothing like a kitten’s rambunctious energy, there’s something about a mellow senior cat that just tugs at the heartstrings. Although they may not have the drive to play and pounce that they once had, there’s still plenty of room in their little kitty hearts for lots of love and snuggles.

Along with that lovable laziness, though, there is also a higher risk that senior cats will develop health issues. Thankfully, though, many conditions are easily treatable if they’re caught early. That’s why it’s important for senior cat parents to include regular wellness checks in their routine and to be familiar with the warning signs of some common health problems.

What Is Feline Hyperthyroidism?

Feline hyperthyroidism is one potentially serious condition, but it’s quite manageable.

Hyperthyroidism in cats is caused by an overproduction of thyroid hormones. It’s a common disorder in senior cats but is rarely seen in younger kitties. About 95% of cats diagnosed with hyperthyroidism are more than 10 years old. 

Knowing the symptoms and calling your veterinarian at the first sign of a problem is the key to curing or managing the condition and allowing your cat to live a long, happy life.

What Does the Thyroid Gland in Cats Do?

Your cat’s thyroid glands help regulate their body’s metabolism and ensure they maintain balanced energy levels and maintain overall good health. It produces two main hormones, thyroxine (T4) and triiodothyronine (T3), which control how your cat’s body uses and stores energy. These thyroid hormones affect a variety of bodily functions: heart rate, body temperature, reproduction, muscle tone, and the rate at which calories are burned.

So what causes the thyroid glands to go haywire? Some theories pointed out by PetMD include fish-flavored canned food diets, flame-retardant chemicals (found in paint, plastic, foam padding, rugs, and so on) used in homes, and rarely, thyroid cancer.

Feline Hyperthyroidism Symptoms

Hyperthyroidism in cats can be tricky to diagnose, since it shares several symptoms with other common health problems, such as diabetes and kidney failure. If you notice any of the following symptoms in your cat, you should definitely schedule an appointment with your veterinarian.

• Increased appetite. Because an overactive thyroid gland speeds up the metabolism, cats with hyperthyroidism are frequently voracious eaters.
• Weight loss. If your cat is losing weight despite a healthy appetite, this could mean something’s wrong with your kitty’s thyroid gland.
• Coat changes. Hyperthyroidism in cats may cause their coat to look unkempt.
• Increased thirst and urination. High levels of thyroid hormone cause the kidneys to produce more urine. Usually, this becomes evident when you are cleaning the litter box. You may notice an increase in the size or number of clumps in your cat’s litter box, or kitty may start going outside the box. Some cats compensate for the increase in urine by drinking more water, but that may not be enough to prevent dehydration.
• Behavior changes. Cats with hyperthyroidism often exhibit unusual behaviors. They may be extremely active, or they may become more aggressive, nervous, or extremely vocal.
• Vomiting or diarrhea. An increased appetite causes some cats to gulp down their food, which can lead to vomiting. Hyperthyroidism also causes food to move more quickly through the intestines, which can cause diarrhea.

How do Veterinarians Test for Hyperthyroidism in Cats?

Diagnosing hyperthyroidism in cats is pretty straightforward: high levels of thyroid hormones in your cat’s bloodstream along with other typical symptoms mentioned above.

Your veterinarian might do some lab tests after finding clinical symptoms of hyperthyroidism in cats and after doing a physical exam. This includes a blood chemistry panel, a urine, test, and an ultrasound of the heart. 

If your cat has an enlarged thyroid gland, they might also do a thyroid scintigraphy, an imaging test where a radioactive substance is injected and then an image of the cat’s neck is taken to visualize the thyroid gland’s activity. This test can determine the size, shape, and position of the thyroid gland and if there are any tumors.

Treating Feline Hyperthyroidism

If your senior cat is presenting symptoms of hyperthyroidism and has been diagnosed, your veterinarian will probably recommend one of three treatment options.

1. Medication

There are several medications on the market that are effective in controlling hyperthyroidism in cats. If your vet recommends this form of treatment, it will not cure your cat’s condition, but it will manage signs of hyperthyroidism and keep him healthy. In order to stay healthy, he will need to take the medication for the rest of his life. Some medications, like methimazole, may also cause side effects like vomiting, fever, lethargy, and so on. If these side effects are too severe for your kitty, ask your veterinarian for alternatives.

2. Surgery

Surgery involves removing the thyroid glands, which results in a cure for most cats. Your veterinarian can determine whether surgery is a safe option for your cat, since anesthesia can be an issue for some senior kitties. Side effects after surgery are rare, but your kitty may experience loss of appetite, vomiting, and tiredness.

Surgically removing the thyroid gland might cause hypothyroidism in your cat (lack of thyroid hormone), so surgery is normally recommended when there’s only one affected thyroid gland.

3. Radioactive Iodine Therapy

Injection with radioactive iodine is effective in curing feline hyperthyroidism. It works because the thyroid gland naturally absorbs iodine, which means the radiation destroys any abnormal thyroid tissue without damaging any other organs or systems.

The downside to radioactive iodine therapy is that it’s a bit more costly than the others, and it also involves a stay in the hospital for several days.

4. Dietary Therapy

Feeding an iodine-restricted diet is a relatively new alternative treatment for hyperthyroid cats. This may be a better call for cats with medical conditions that would make the other treatment options difficult or impossible to do. However, this is not a cure, and your kitty will likely require lifelong treatment. 

Research for this potential treatment is still ongoing, so if this alternative appeals to you, consult your veterinarian if it’s possible for your cat with hyperthyroidism. Since this is a diet with controlled iodine content (0.2ppm), it should be given exclusively—no cat treats or other cat food or human food.

Hyperthyroidism and Kidney Disease

Untreated hyperthyroidism in cats can lead to a number of other problems, including heart disease and high blood pressure.

If it’s not caught early, high blood pressure can lead to damage of the kidneys. On top of that, hyperthyroidism can make kidney disease harder to detect. This is because hyperthyroidism can actually improve kidney function because it causes increased blood flow. Some cats experience a worsening of their kidney symptoms after they begin treatment for hyperthyroidism.

If your cat is being treated for hyperthyroidism, talk to your vet about monitoring his kidney function. An older cat with hyperthyroidism often has kidney disease as well. Early detection is key in successfully treating kidney disease.

If your cat’s kidneys are functioning well, here are a few things you can do to promote kidney health at any age.

• Keep the litter box clean and accessible. This will make it easier for your cat to urinate when he feels the need.
• Take your cat for regular checkups. Don’t wait until you notice symptoms of illness to bring your cat to the vet. Routine screenings and checkups can reveal problems early, making it much more likely that you’ll be able to treat them successfully. Younger cats should see their veterinarian once a year, and many veterinarians recommend that senior cats be seen every 6 months.

What Is the Prognosis for Hyperthyroid Cats?

The good thing about feline hyperthyroidism is that it is treatable, and cats who are diagnosed and treated early have a good chance of living long, happy lives. Outcomes following most treatment alternatives for cats with hyperthyroidism are great, and cats with managed diets or medications generally do well.

Left undiagnosed, however, it becomes much more serious – even fatal. That’s why it’s so important to visit your veterinarian regularly and to schedule an appointment at the first sign of any change in your cat’s overall health.