Hyperthyroidism in Cats: Symptoms, Treatments & Prevention

Hyperthyroidism is one of the most common diseases in cats. In fact, it’s the most prevalent glandular disease to affect our feline friends.

All cats have two thyroid glands located in their neck, and these play an essential part in regulating their metabolic rate. Hyperthyroidism, also known as thyrotoxicosis, is characterized by an increase in thyroid hormones (T3 and T4), which causes an increase in metabolic rate.

Because these hormones affect many other organs in the body, hyperthyroidism is often the cause of felines’ health problems.

Here, we’ll outline everything you need to know about this condition, including signs of hyperthyroidism, symptoms, and treatments.

What Are the Symptoms of Hyperthyroidism in Cats?

The most common symptom of hyperthyroidism is weight loss, and increased thyroid hormones cause it. Between 95 and 98% of cats with hyperthyroidism display weight loss, most often due to muscle wasting.

Note that weight loss does not necessarily mean that your pet will be underweight, but will have lost a significant amount of weight relative to their normal weight.

Alongside weight loss and an increase in appetite, other signs of hyperthyroidism include:

  • Extreme thirst or an increased appetite
  • Hyperactive tendencies
  • Increased urination
  • Panting
  • Increased vocalization (which often occurs at night)
  • An increased or unusual pattern of coat shedding
  • Diarrhea and vomiting
  • Unkempt appearance
  • Enlarged thyroid glands

How Is Hyperthyroidism Diagnosed in Cats?

Due to the fact that cats with hyperthyroidism tend to be older, they often have concurrent illnesses such as inflammatory bowel disease, diabetes, and kidney failure. These can be caused or exacerbated by increased levels of thyroid hormones from the thyroid gland.

Many of the signs of hyperthyroidism overlap with these diseases’ symptoms, making diagnosis complicated. This means that a number of tests and examinations are generally needed to diagnose a hyperthyroid cat.

Here’s how veterinarians typically conduct the diagnosis:

Physical Examination

When a feline with suspected high thyroid hormone levels is taken to the vet, a veterinarian will start by conducting a physical examination. This involves palpating the neck area to see whether an enlarged thyroid gland or any abnormal thyroid tissue can be detected. They may also check the cat’s blood pressure and heart rate.

T3 and T4 Analysis

If the veterinarian believes there may be a problem with the cat’s thyroid gland, they’ll likely order an analysis of T3 and T4 hormone levels, as well as blood tests.

While most cats with hyperthyroidism will have a higher than normal level of thyroid hormone T4, a small number of cats with hyperthyroidism will still be within the normal range for T4.

A feline with a suspected thyroid problem that displays normal levels of T4 may need additional testing.

Urine and Blood Test

Because hyperthyroidism can cause other conditions, it’s important that the cat’s general health is checked when there is a problem with the thyroid glands and/or high thyroid hormone levels.

A urinalysis and complete blood test set should provide the veterinarian with enough information to build a picture of your pet’s overall health. Particular attention should be paid to the kidneys and heart, as the high levels of thyroid hormones caused by hyperthyroidism often predispose them to issues with these organs.

How to Treat Hyperthyroidism in Cats

There are a number of different treatments for hyperthyroidism available. The most appropriate treatment depends on individual circumstances involving both the cat and the owner.

Their overall health is the main factor in determining the best treatment path. Meanwhile, the financial situation and ability to medicate the feline regularly are important considerations, too.

Feline thyroid problems can be treated in the following ways:



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