Hyperthyroidism in Cats

What is hyperthyroidism?

Hyperthyroidism is a common disease in cats, and mostly affects middle-aged and older cats. It is characterized by the overproduction of thyroid hormone from an enlarged thyroid gland in a cat’s neck. Cats have two thyroid glands and they play a vital role in regulating the body’s metabolic rate. The overproduction of the thyroid hormone causes an increase in metabolic rate.

In most cases, enlargement of thyroid glands is caused by a non-cancerous tumor called an adenoma. Some rare cases of hyperthyroid disease are caused by malignant tumors known as thyroid adenocarcinomas.

Thyroid hormones affect nearly all the organs in the body; therefore, thyroid disease often causes secondary problems.

Although the cause of feline hyperthyroidism is not known, possible contributing factors include deficiencies or excesses of certain compounds in the diet and chronic exposure to thyroid-disrupting chemicals in food or the environment.

What are the symptoms?

The most common clinical signs of hyperthyroidism are weight loss, (despite) an increased appetite, and increased thirst and urination. They may develop periodic vomiting or diarrhoea, and fur may appear unkempt, matted or greasy. In some cats, anorexia develops as the disease progresses. Affected cats are often restless and may become cranky or aggressive. It is also common for hyperthyroid cats to show increased vocalizing, especially at night.


A Vet who suspects a cat has a thyroid problem will usually conduct a physical examination and palpate the cat’s neck area to check for an enlarged thyroid gland. The cat’s heart rate and blood pressure may also be checked. A blood test can show an elevated level of the thyroid hormone T4. A small percentage of cats with hyperthyroidism may show T4 levels within the normal range. If that is the case, additional tests may be recommended. Since hyperthyroidism can lead to other conditions, it is important the general health is evaluated, with particular focus on the heart and kidneys.

Secondary problems

Elevated thyroid hormones stimulate an increased heart rate and a stronger contraction of the heart muscle. This can result in a thickening of the left ventricle of the heart over time.

Hypertension, or high blood pressure, is another potential complication of hyperthyroidism, and can cause additional damage to several organs, including the eyes, kidneys, heart, and brain.

Treatment by Vets

Vets usually work with the following three options in treating Hyperthyroidism.

Medication – Aimed at reducing the Thyroid activity medication can be very effective. Unfortunately, about 10%-15% of cats will suffer side effects, such as loss of appetite, vomiting, lethargy, and occasionally blood cell abnormalities.

Radioactive iodine therapy – 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 is seen as the safest treatment of the three here. However also this treatment can have side effects.

Surgical removal of the tumor – most hyperthyroid cats have benign, well-encapsulated tumors that are easily removed. Surgery usually results in a cure, but anesthesia can be challenging in these older patients whose disease may have affected their hearts and other organs.

Homeopathic treatment options

There are Homeopathic remedies available that can help balance the overacting thyroid and, in combination with a constitutional remedy can support the overall thyroid health. It is an easy and cost-effective way to maintain your cat’s health.

Ref: www.vet.cornell.edu – hyperthyroidism-cats / Pets.webmd.com / vcahospitals.com/know-your-pet/hyperthyroidism-in-cats


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The information contained in this website is not intended to replace guidance from your veterinarian. Bowen Therapy and Homeopathy are complementary to veterinary treatment and the general care of the animal.