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Thyroid Problems In Cats: The Likely Cause

Two Thyroid Issues Cats Can Face, and Which is Most Common

By Lauren Leonardi . October 18, 2013 | See Comments

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Hyperthyroidism is an ailment more common in cats than in dogs. It can cause major health problems for your cat if left undiagnosed and untreated. Learn the causes of thyroid problems in cats and the options available.

Thyroid problems in cats stem from either an over abundance or a deficiency of thyroid hormones. The prior -- hyperthyroidism -- is by far the more common feline thyroid condition, and it’s the condition this article will focus on. Learn about why a cat’s body relies on the thyroid, signs that may indicate a thyroid problem, and what treatment might look like if your cat is diagnosed with hyperthyroidism.

What’s a Thyroid?

The thyroid a little gland, shaped a bit like a bowtie, that lives in the neck of every cat (and dog, and human, and many animals). The thyroid secretes two hormones called thyroxine and triodothyronine, which help regulate important bodily functions like metabolism and organ functions.

What Is Hyperthyroidism in Cats?

Hyperthyroidism occurs when the thyroid secretes too much thyroxine. The excessive concentration of hormones moving around in the bloodstream can cause an overactive metabolism, which can strain other organs and have a ripple effect of serious health problems including kidney and heart failure.

Can All Cats Develop Hyperthyroidism?

It’s estimated that 2 in 100 cats will develop the condition, but usually in later life. Hyperthyroidism is most common in cats who are 10 years or older.

Common Signs of Thyroid Problems in Cat

  • A cat suffering from hyperthyroidism will often lose weight, even though they’re eating the same amount of food.
  • Likewise, your cat may seem hungrier, and may eat more without gaining weight.
  • Behavior changes are common, especially those that skew toward greater hyperactivity -- increased friskiness and vocalization are common.
  • Increases in the amount of water consumed, as well as increased urination, are both signs that hypothyroidism could be an issue.

Diagnosis of Thyroid Problems in Cats

Once you’ve described the symptoms to your veterinarian, they may decide a blood test is in order. A blood test is the most common and effective method of diagnoses for thyroid problems in cats.

The blood test, called T4, will examine thyroid hormone levels in your cat’s body. If hyperthyroidism is present, this test will usually be conclusive. In some cases, the T4 test won’t be enough for a firm diagnosis, so your vet may take more blood to do a test called T4 - Free, which looks further for indications of hyperthyroidism.

Because hyperthyroidism is most commonly found in older cats, it’s possible and even likely that hyperthyroid is not the only ailment at play. Other conditions geriatric cats commonly encounter can share symptoms with hyperthyroidism, like diabetes and kidney failure. T4 is the best method to determine or rule out an overactive thyroid.

Treatment of Thyroid Problems in Cats

Hyperthyroid cats can be treated with antithyroid drugs. The most common antithyroid drug for cats is Methimazole. The brand name version of this drug is Tapazole. The pill is typically administered once or twice a day. It can be (literally) a bitter pill to swallow, so it may be necessary for pet parents to hide the pill inside treats or food.

  • The medication will need to be dispensed every day for the rest of the cat’s life.
  • Symptoms should improve within 2-3 weeks.
  • Some cats experience side effects like continued weight loss, itchiness, or lethargy. Sometimes these side effects will pass. Sometimes they won’t, and use of the drug will be discontinued.

Removal of the thyroid through surgery is also an option. Surgery is, of course, invasive, and can be difficult for an older cat who may already be suffering from other health problems. However, the benefits of surgery do sometimes outweigh the stress of daily pill administration and regular blood checks.

Diet After Diagnosis

A high protein, low carbohydrate diet is recommended for all cats of all stages of wellness. This balance of more protein/fewer carbs becomes even more important when a cat is diagnosed with hyperthyroidism. Discuss diet changes with your veterinarian.

What About Hypothyroidism?

This condition is highly unlikely to afflict cats, but it does happen occasionally. In humans and dogs, hypothyroidism is often inherited. In cats, however, the condition will usually only occur if damage has been done to the thyroid gland, like during surgery, for example. Hypothyroidism can also occur as a result of hyperthyroid treatment through the use of radioactive iodine.

Hypothyroidism in cats will present with weight gain, listlessness, and a dull and dry coat. However, unless the aforementioned trauma has affected your cat, these symptoms are likely pointing to another condition.

More on Cat Health

How To Know if Your Pet is Underweight
The Best Senior Cat Pet Supplies
Managing Treatment for Diabetic Cats

This information is for informational purposes only and is not meant as a substitute for the professional advice of, or diagnosis or treatment by, your veterinarian with respect to your pet. It has, however, been verified by a licensed veterinarian for accuracy.

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Hyperthyroidism at a glance

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  • 1A condition in which the thyroid gland makes a higher concentration of hormones than it should.
  • 2An overactive thyroid can cause weight loss, restlessness, and hyper behavior.
  • 3Hyperthyroidism can be treated through the daily administration of pills.