What is Hyperthyroidism in Cats?

What is Hyperthyroidism in Cats?

What is it?

Hyperthyroidism is a common endocrine disorder in cats caused by an overactive thyroid gland. As a result, the thyroid gland produces excessive amounts of thyroid hormones, leading to various health problems. Hyperthyroidism can be challenging to diagnose and manage and requires ongoing care and monitoring by a veterinarian.

How is it Treated?

The treatment of Hyperthyroidism in cats typically involves medications, dietary changes, or a combination of both. Medications may include methimazole or carbimazole, which work to decrease the production of thyroid hormones. Some cats may also benefit from a special diet designed to reduce the intake of iodine necessary for thyroid hormone production. In some cases, surgical or radioactive iodine therapy may be required to manage Hyperthyroidism.

Breed Predispositions

Siamese Himalayan Persian Domestic Shorthair Domestic Longhair


When Oliver, a charming Ragdoll cat, started showing signs of weight loss and increased appetite, his owner, Grace, knew something was off. Worried about these unexpected changes, she took Oliver to their trusted veterinarian for a thorough check-up. After conducting blood tests, the veterinarian diagnosed Oliver with hyperthyroidism, a common hormonal disorder in cats.

Hyperthyroidism in cats is an endocrine disorder with too much thyroid hormone circulating in the blood. This excess thyroid hormone leads to symptoms such as weight loss, heart palpitations, anxiety, and nervousness. In addition, in some cases, cats with Hyperthyroidism may experience swelling in the neck area due to enlargement of the thyroid gland.

There are four types of Hyperthyroidism: toxic nodular goiter (TN), diffuse goiter (DG), Graves’ disease, and carcinoma (CA).

  • Toxic nodular goiters are tumors that grow in the thyroid gland. These tumors can be benign or malignant. Benign toxic nodules usually appear as large lumps under the skin, while malignant ones tend to spread into surrounding tissues. Malignant toxic nodules are rare in cats, but benign ones are common. Toxic nodules are typically found during routine physical exams.
  • Diffuse goiters are thyroid nodules that appear diffusely over the entire gland. They are usually benign tumors that grow slowly over time. Diffuse goiters are typically found in older animals, especially female dogs and cats.

While diffuse goiters aren’t dangerous, they can affect your pet’s health. Some pets develop symptoms related to Hyperthyroidism, including weight loss, increased appetite, excessive energy, and urination problems. However, these signs can be mistaken for other conditions, so it’s important to rule out other causes of weight loss before diagnosing Hyperthyroidism.

  • Graves’ disease is a condition that causes hyperactivity in the thyroid gland. Hyperthyroidism occurs when the thyroid produces too much hormone, causing symptoms like weight loss, increased appetite, heart palpitations, and anxiety.

There are two types of Graves’ disease: exogenous and endogenous. Exogenous refers to autoantibodies against thyroglobulin, while endogenous relates to antibodies against TSH receptors. Both forms of the disease require treatment with anti-thyroid drugs.

  • Carcinomas begin in cells, part of our body’s immune system. Carcinomas are classified based on the type of cell they originate from. Some cancerous tumors develop from epithelial tissue, while others arise from connective tissues.

Epithelial tissue includes skin, mucus membranes, glands, and other organs that line cavities within the body. Connective tissue includes tendons, ligaments, bones, cartilage, blood vessels, nerves, and muscles.

Where are Your Cat’s Thyroid Glands?

Cats have a single thyroid gland that is located near the windpipe. This gland produces three main types of hormones: thyroxine (T4), triiodothyronine (T3), and reverse triiodothyronine(rT3). These hormones regulate metabolism, growth, reproduction, and nervous system function. In addition, cats produce some of their iodine from dietary sources, which helps maintain healthy levels of thyroid hormone production.

Where are Your Cat's Thyroid Glands?

What Do Your Cat’s Thyroid Glands Do?

The thyroid gland regulates body temperature, heart rate, and cardiac output and controls how much energy is stored in fat cells.

Your cat’s thyroid gland produces several important hormones essential for normal body functions. For example, thyroid hormones help control how fast your cat burns calories, regulate blood sugar levels, maintain healthy bones, muscles, hair, nails, teeth, and skin, and help maintain proper brain development.

When you feed your cat properly, it will make enough thyroid hormone to meet its needs. However, if your cat doesn’t eat enough, it won’t make enough thyroid hormone to meet its daily requirements. As a result, your cat will begin losing weight.

Cats who overeat often become overweight. They’re prone to developing obesity because their bodies don’t use stored fat efficiently. As a result, their thyroid glands enlarge and overproduce thyroid hormone. Enlarged thyroid glands cause your cat to retain water, leading to increased weight.

Causes of Feline Hyperthyroidism

In most cases, it is caused by an overactive thyroid gland. However, sometimes the thyroid gland produces too little thyroid hormone driving a condition known as hypothyroidism.

Cat’s hyperthyroidism usually develops due to an autoimmune disorder called feline hyperadrenocorticism (HAC). HAC is caused by the body attacking itself, resulting in inflammation and damage to the adrenal glands.

Cats with Hyperthyroidism may also develop diabetes mellitus. Diabetes affects the ability of blood vessels to transport glucose into cells and use it for energy.

As a result, the pancreas secretes large amounts of insulin to help regulate blood sugar levels. When the thyroid gland becomes hyperactive, it increases the number of thyroid hormones produced. Insulin does not work well in the presence of high levels of thyroid hormones because the thyroid gland uses most of the insulin produced by the pancreas.

As a result, blood sugar levels rise and become unstable. In addition, the liver cannot process fats properly, leading to fatty deposits around the kidneys.

What Are Breeds Prone to Hyperthyroidism?

What Are Breeds Prone to Hyperthyroidism?

Hyperthyroidism is most common in older cats, especially those over ten. It occurs less frequently in younger cats. Several breeds of cats are prone to Hyperthyroidism, including the Maine Coon, Persian, Ragdoll, Siamese, Sphynx, and Turkish Angora. These breeds tended to be larger than others and predisposed toward obesity.

It’s also important to remember that certain breeds are more likely to develop Hyperthyroidism, but it can happen to any breed. So as long as your pet eats healthy food and exercises regularly, they shouldn’t have any problems.

What are the Symptoms of Hyperthyroidism in Cats?

Symptoms of Hyperthyroidism in cats usually appear as weight loss despite increased appetite, excessive urination, aggression, depression, restlessness, and difficulty breathing. These are just some of the possible symptoms.

Other signs of Hyperthyroidism include vomiting, diarrhea, muscle wasting, lethargy, lack of coordination, seizures, heart problems, kidney failure, high blood pressure, and enlarged glands. If left untreated, Hyperthyroidism can lead to death.

Diagnosis for Cats with Hyperthyroidism

To diagnose Hyperthyroidism, veterinarians perform a physical examination, blood tests, thyroid ultrasound scans, and Nuclear Medicine scans. In addition, your vet will check for evidence of organ dysfunction, such as an irregular heartbeat, poor muscle tone, rapid breathing, and changes in behavior.

  • Blood test

Thyroid-stimulating hormone (TSH), free thyroxine (fT4), and total triiodothyronine (tT3). TSH checks how well the pituitary gland is producing thyroid hormones. fT4 measures what level of thyroid hormones are circulating in the bloodstream. tT3 checks for abnormalities in thyroid function.

  • Nuclear Medicine Scan

Technetium-99m pertechnetate is injected into the vein. After about 30 minutes, images are taken to see if the thyroid gland is usually working.

  • Ultrasound

An ultrasound uses sound waves to produce pictures of internal organs. A small amount of contrast material is given intravenously to highlight areas inside the body.

Treatments Options for Hyperthyroidism

Treatment option includes medication, radioiodine therapy, and surgery. These treatments depend on the type of hyperthyroid syndrome present. 

  • Medications are typically prescribed for your cat’s entire life. They work by blocking the production of thyroid hormones. For example, your vet might prescribe one of the following medications: propylthiouracil, methimazole, carbimazole, or iodine 131. These drugs must be administered daily for the rest of your pet’s life.
  • Radioiodine therapy is an effective way to manage Hyperthyroidism in some cats. Approximately 95% of all hyperthyroid cases are curative within three months of radioiodine therapy. It involves injecting patients with radioactive iodine. The radioactive iodine attaches itself to the thyroglobulin protein found inside the thyroid cells.

Thyroglobulin is a large protein that holds onto iodine. When the radioactive iodine attaches to the thyroglobulin, it becomes radioactive and destroys the thyroid cells. This causes the thyroid gland to shrink and stop producing excess thyroid hormones. A second injection of radioiodine is given about six months later.

  • Surgery is another viable option if medication isn’t working. In this case, your veterinarian will cut out the affected thyroid gland. Surgical thyroid gland removal is typically recommended for cats with toxic nodular or diffuse goiter. However, surgery carries risks such as bleeding, infection, and scarring.

Cats That Have Been Diagnosed With Hyperthyroid Disease Should Receive Regular Monitoring after Treatment

After treating Hyperthyroidism in cats, veterinarians recommend monthly blood tests to monitor thyroid function and how well their bodies respond to the medication. These tests measure levels of T4 and T3 hormones in the bloodstream.

It’s recommended that owners continue to monitor their pet’s health after treatment. Monitoring includes checking for signs of lethargy, weight loss, vomiting, diarrhea, increased appetite, and other hypothyroidism-related symptoms.

Frequently Asked Questions

The life expectancy of a cat suffering from Hyperthyroidism depends on many factors, such as age, weight, breed, sex, health status, and treatment. The average lifespan of a cat with Hyperthyroidism is 12 years. However, some cats live longer than this, while others die younger.

The best food to feed a Hyperthyroid Cat is a balanced diet that contains enough protein, fat, carbohydrates, vitamins, minerals, fiber, antioxidants, omega-3 fatty acids, probiotics, enzymes, amino acids, etc. A healthy diet should contain at least 20% protein, 10% fat, 30% carbs, 5% fiber, and 2% water. Feeding a hyperthyroid cat dry food is recommended because wet foods make their skin oily and increase the risk of hair loss. In addition, dry food is easier to digest than wet food, making it less likely to cause stomach upset.

The cost of treating Hyperthyroidism in dogs varies from $100-$400 per month, depending on the severity of the condition. Cat treatment costs are usually around $50-$200 per month. However, it’s worth spending money if you want your cat to live longer.

You can help prevent Hyperthyroidism by following some basic guidelines.

  1. Make sure your pet gets plenty of exercise. Exercise helps keep your pet healthy and reduces stress levels.
  2. Feed your pet a diet low in carbohydrates and rich in protein. A balanced diet provides essential nutrients needed for proper growth and development.
  3. Give your pet a daily dose of vitamin B6. Vitamin B6 helps maintain normal metabolism and energy levels. Finally, avoid giving your pet foods containing wheat products. Wheat contains gluten, which can trigger inflammation in pets with allergies.

Cats with Hyperthyroidism can suffer from kidney failure if they do not receive treatment. Kidney disease is one of these side effects. The kidneys filter waste products from the blood and produce urine. If you have Hyperthyroidism, your kidneys may become damaged because they work harder than usual.

Your cat’s kidneys may get swollen if this happens. You should immediately see your veterinarian if your cat shows any signs of kidney disease.

Hyperthyroidism can lead to heart problems, kidney failure, liver damage, seizures, coma, and even death. Unfortunately, these conditions can be fatal without immediate medical attention. Therefore, it is essential to seek veterinary care immediately if your cat has symptoms of Hyperthyroidism.

Hyperthyroidism is a condition in which the thyroid gland produces too much hormone. Some possible causes are hyperactivity of the thyroids, an autoimmune process (in which your immune system attacks your own body), and tumors or other abnormalities in the thyroid gland.

Untreated Hyperthyroidism can lead to several serious health problems, including heart failure, stroke, and even death. If you are unsure if your cat has Hyperthyroidism or thinks he may be ill due to the condition, you must take him to a veterinarian as soon as possible.

A cat with Hyperthyroidism may feel restless and energetically high. They may pace or move constantly, and their coats become oily and thickened. As a result, their appetite might be increased, leading to weight loss or overeating. Sometimes, a cat with Hyperthyroidism might stop eating altogether due to an enlarged stomach or vomiting.

The final stages of Hyperthyroidism in cats involve a gradual and complete loss of appetite, diarrhea, muscle weakness, and a decreased sense of smell. Death may eventually follow if the condition is not treated.

The course of Hyperthyroidism in cats can be variable, and some cats may experience a gradual increase in their symptoms while others may experience an abrupt worsening of their condition. Some signs that might suggest that the cat’s Hyperthyroidism is getting worse include more frequent vomiting, increased appetite, weight loss, lethargy or lack of energy, and changes in coat color.

Some cats can live on thyroid medication for a year or more, while others may only be able to take it for a few months. The time your cat can take the drug will depend on their general health and how well they react to the treatment.

Some foods that may be contributory include: raw meat (especially chicken), seafood, eggs, milk, and certain grains. Cats are particularly susceptible to developing Hyperthyroidism if they have a history of eating these foods in excess or if their metabolism is fast-paced due to other health problems.

Diarrhea can be a side effect of many medications and infectious diseases in cats. However, the most likely cause of diarrhea in cats with hyperthyroidism is an imbalance in their gut flora, which could lead to the overgrowth of bacteria or yeast. This condition typically results in loose stools and often requires antibiotics to treat.

Anemia is due to a lack of iron stores; it may be exacerbated in cats with Hyperthyroidism. Additionally, inflammation and redness associated with Hyperthyroidism can reduce blood flow and increase the risk of anemia. Therefore, your veterinarian should perform a complete blood count (CBC) to determine whether any other potential causes for your cat’s anemia must be addressed simultaneously.

Cats with Hyperthyroidism may be more prone to developing eye problems, including vision loss, due to causes such as uveitis or glaucoma. Therefore, if your cat has recently started displaying any signs of visual impairment (such as decreased sight ability or blindness), it would be best to consult a veterinarian for further evaluation and treatment.

Yes, Hyperthyroidism can cause loss of appetite. However, this may be due to many different reasons, including anxiety caused by high blood pressure and heart problems common with Hyperthyroidism.

Several eye problems, such as horizontal strabismus (eyes not aligned in the same direction), may occur in cats with Hyperthyroidism. An eye exam and assessment by an ophthalmologist may be necessary to determine the extent of these problems.

Here are some natural treatments that have been successfully used by many pet owners include:

  1. Dieting/limiting food intake: One of the simplest ways to help manage Hyperthyroidism in cats is by dieting or restricting their food intake. Cats with Hyperthyroidism can often reduce or even eliminate their symptoms by restricting their caloric intake.
  2. Exercising: A regular exercise regimen can help control the symptoms of Hyperthyroidism in cats. Exercise helps to release endorphins, which have an anti-inflammatory effect and can reduce a cat’s discomfort from Hyperthyroidism.
  3. Herbal treatments: Many pet owners swear by using herbal remedies to treat Hyperthyroidism in their cats. Some popular herbs used as natural supplements to treat Hyperthyroidism include black walnut extract, guarana, garlic, ginger, and turmeric.

No definitive answer exists on whether cat hyperthyroidism can cause deafness, but it is possible. If the thyroid gland enlarges and puts pressure on other organs, such as the ears, it may lead to hearing loss. More research is needed to confirm this potential connection.

Hyperthyroidism is not typically inherited in cats but can be due to various causes. Some of these include feline immunodeficiency virus infection and tumors.

A cat may experience weight loss, respiratory problems, and an increased appetite. If untreated, the condition can lead to heart problems and eventually death.

The cost of treating hyperthyroidism varies considerably based on the specific condition and treatment plans. However, general estimates put the average cost of treating a hyperthyroid cat at around $500-$1,000.

Yes, euthanasia should be considered for cats with thyroid problems when the cat is not improving, and there are no other signs of life.

Disclaimer: The information provided on this veterinary website is intended for general educational purposes only and should not be considered as a substitute for professional veterinary advice, diagnosis, or treatment. Always consult a licensed veterinarian for any concerns or questions regarding the health and well-being of your pet. This website does not claim to cover every possible situation or provide exhaustive knowledge on the subjects presented. The owners and contributors of this website are not responsible for any harm or loss that may result from the use or misuse of the information provided herein.

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