Hyperthyroidism In Cats: Facts You Need To Know About The Condition


The hyperthyroidism in cats is a commonly diagnosed condition, specifically in the senior cats. The condition results in the superfluous levels of the thyroid gland, as well as circulate through the affected bloodstream of the cat. Give this article a read and get to learn more about hyperthyroidism in cats and more!

Hyperthyroidism in Cats: What is this condition?

Hyperthyroidism is a common illness in cats and generally afflicts the middle-aged and senior cats.

It is also known as the thyrotoxicosis, this condition is from an engorged thyroid gland in the neck of the cat. In most of the cases, the engorgement of the thyroid glands is due to a non-cancerous tumor known as the adenoma. Some of the rare cases of the hyperthyroidism are due to a malignant tumor that is known as the thyroid adenocarcinomas. Even though the cause of the feline hyperthyroidism is not that known, possible contributing factors include excesses or deficiencies of particular compounds in diets, as well as the chronic exposure to thyroid-disturbing chemicals in the environment or in foods.

Thyroid hormones may affect almost all the organs in the body. Hence, thyroid disease often causes secondary conditions.

The condition is also the most common glandular disorder in the cats. Further, it is most often due to an excessive concentration of the circulating thyroxine-A hormone or the T4 hormone in the bloodstream

Causes of Hyperthyroidism

The hyperthyroidism in cats is due to a benign tumor on the cat’s thyroid gland, which overproduces T4 levels. It is so important to bear in mind that these particular tumors are all nonthreatening and denote a particular type of goiter, instead of a type of cancer. Lesser than 3 to 5% of the cats who have the condition have cancerous thyroid tumor.

A lot of people know what triggered the cat’s thyroid gland in order to grow some kind of tumor, nonthreatening or something else. Furthermore, there is a strong connection between the consumption of canned food, as well as the development of the condition later in life. In the actual fact, cats that eat just canned foods, which are from the pop-top cans, have 5x risk of getting hyperthyroidism, in relation to cats that eat just dry cat foods.

Cat Breeds Prone to Hyperthyroidism

The hyperthyroidism may happen in whatever breed of cat, female or male, yet happens almost utterly in the older cats. Less than 6% of the cases are younger than 10 years old. Moreover, the average age at the onset is in between 12-13 years.

Symptoms of Hyperthyroidism

An increase in the appetite and weight loss are among the most common clinical signs of hyperthyroidism. Furthermore, weight loss is seen in about 95-98% of the cats who have hyperthyroidism, and a robust appetite in 67-81%. Increase in shedding, hyperactivity, increase in urination, excessive thirst, diarrhea, panting as well as frowzy appearance have been reported as well. Moreover, vomiting is seen in approximately 50% of the cats who have the condition. The clinical signs are the result of the effect of the increase in T4 levels on certain organ systems.

Prognosis of Hyperthyroidism

Due to several common illnesses of the older cats –chronic kidney failure, intestinal cancer, inflammatory bowel disease, and diabetes –share some clinical signs of the condition, a series of test is necessary. Furthermore, a CBC test, urinalysis, and chemistry panel may not be able to diagnose the condition, yet they may surely rule out the kidney failure and diabetes. Moreover, the cats with hyperthyroidism might have normal findings on their urinalysis and CBC, yet the chemistry panel often shows an elevation of various liver enzymes.

In so many causes of the condition, a definitive prognosis of the condition is based on a simple blood test, which shows increased T4 levels in the bloodstream. Unluckily, between 2-10% of cats with hyperthyroidism may have normal levels of T4. Perhaps, an explanation for this is that in the mild cases, the T4 levels may fluctuate inside and outside the normal range. One more is that concurrent illness may suppress elevated levels of T4, thus lowering them in the high normal or normal range and fooling the vet to thinking that the case of a cat is normal. Since they’re geriatric cats, simultaneous illness is somewhat common, and prognosis of the condition may be tricky.

Treatments for Cat Hyperthyroidism

Here are some of the possible treatments of hyperthyroidism in cats:

  • Feeding a diet that’s restricted in iodine. This includes methimazole treatment –this particular alternative isn’t treatable at all and the cat may need lifelong treatment.
  • Medical treatment with methimazole is perhaps the most common choice of treatment. This medication may be administered by mouth or may be formulated in a transdermal gel that may be applied to the cat’s ear.
  • Surgical operation of the diseased thyroid gland. This is curative, but cats must also be monitored for possible hypothyroidism afterward.


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