Hyperthyroidism in Cats and Treatment Options

Hyperthyroidism is a common condition in older cats, typically resulting in noticeable weight loss and changes in behavior. While several treatment options are available, including surgery to remove the affected thyroid tissue, be sure to weigh the risks and benefits.

What Is Hyperthyroidism in Cats?

Hyperthyroidism occurs when the thyroid gland produces excessive thyroid hormone, which controls the body’s metabolism. The thyroid gland is located near the cat’s neck and comprises two parts on either side of the windpipe.

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Most cases of hyperthyroidism in cats are caused by benign (non-cancerous) growths within the thyroid gland, which result in the overproduction of hormones. This condition is most common in cats over eight years old, affecting about 10% of cats in this age group. Thankfully, aggressive thyroid cancers are rare, accounting for less than 5% of cases.

Symptoms of Hyperthyroidism in Cats

The overproduction of thyroid hormone affects various systems in the body, such as the heart, kidneys, skin, and muscles. Cats with hyperthyroidism may show the following symptoms:

• Weight loss: Despite an increased appetite, affected cats often lose weight.
• Increased appetite: Cats may eat more than usual but still lose weight.
• Behavioral changes: Cats might become more vocal, hyperactive, and sometimes more aggressive.
• Goitre: An enlarged thyroid gland can be seen or felt in the neck area.
• Increased heart rate: Cats may develop an abnormally fast heart rate.

Hyperthyroidism can also contribute to other health issues, including heart enlargement (cardiomyopathy), high blood pressure, inflammatory bowel disease, and bladder infections. In some cases, it may also mask underlying kidney disease, which can worsen once the thyroid condition is treated.

How Is Hyperthyroidism Diagnosed?

Diagnosis typically starts with a blood test to measure thyroid hormone levels. If the thyroid levels are elevated above the normal range, hyperthyroidism is confirmed. In some cases, particularly in the early stages, the condition may not be easily diagnosed with a single blood test. In these cases, additional tests may be necessary, including tests for kidney function and urine analysis to determine the most appropriate course of treatment.

Treatment Options for Hyperthyroidism

There are four main treatment options for hyperthyroidism in cats: medication, diet, radioactive iodine therapy, and surgery. Each option has its advantages and limitations.

1. Anti-Thyroid Medication

Anti-thyroid medication is often the first treatment option. It works by blocking the production of thyroid hormones. This treatment is available in tablet form, liquid, or as a gel applied to the skin inside the cat’s ears. The downside of medication is that it does not cure the condition, so the cat will need to be treated for life with regular blood tests to monitor hormone levels. Common side effects of medication include loss of appetite, vomiting, and skin reactions. While affordable in the short term, the cost can accumulate over time.

2. Iodine-Restricted Diet

For cats that do not tolerate medication, an iodine-restricted diet may be an option. This food limits the production of thyroid hormones and requires the cat to eat only the special food with no additional treats or other food. Although it is effective, some cats may refuse to eat this diet, and it can be more expensive than regular food.

3. Radioactive Iodine Therapy

Considered the “gold standard” for treating hyperthyroidism, radioactive iodine therapy offers a potential long-term cure. The treatment involves administering a radioactive form of iodine to destroy the overactive thyroid tissue. This procedure requires a stay at a specialist hospital for several days due to the radioactive nature of the treatment. Most cats respond to the therapy within 3 to 6 months, although a small percentage may require a second round. This is the most expensive treatment but is the most effective and carries fewer long-term risks than surgery.

4. Surgery (Thyroidectomy)

Surgery to remove the affected part of the thyroid gland, known as a thyroidectomy, can provide a permanent solution for hyperthyroidism. The procedure is typically performed under general anesthesia and involves removing the abnormal thyroid tissue. The surgery generally takes about 45 minutes and is usually done without major complications. However, there are risks, including low blood calcium levels (hypocalcemia) if the parathyroid glands are affected during the procedure. Most cats recover well with appropriate care, but there may be a need for calcium supplementation following surgery.

Is Surgery the Right Option for My Cat?

The decision to opt for surgery depends on several factors, including the cat’s overall health, age, and the presence of other conditions like kidney or heart disease. While surgery is effective, it may not be suitable for all cats, particularly those with other significant health issues. Your veterinarian will be the best person to guide you through the decision-making process and recommend the most appropriate treatment for your cat.

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Bottom Line

Hyperthyroidism in cats is a manageable condition, and with the right treatment, cats can lead happy, healthy lives. Each treatment option offers distinct benefits and challenges. It’s important to consult with your vet to determine the best course of action based on your cat’s individual health needs.