Hyperthyroidism in Cats: Treatment Options

Once your cat is diagnosed with hyperthyroidism, the next step is choosing the best treatment. Fortunately, several treatment approaches to hyperthyroidism in cats exist, and your veterinarian can help you decide which one is most suitable for you and your cat.

Treatment for Hyperthyroidism in Cats¹

The goal of treatment for hyperthyroidism is to bring thyroid hormone levels back to normal while protecting the kidneys and overall health. For hyperthyroidism in cats, treatment is recommended, even for cats with other conditions like kidney disease. Before starting, your veterinarian will check kidney function, blood pressure and urine protein to help determine the safest option.

There are four main treatments for feline hyperthyroidism and cats with overactive thyroid symptoms:

1. Radioactive Iodine Therapy

This is most often a one-time treatment that safely destroys overactive thyroid tissue.

Key Benefits:

• Considered the most effective and permanent treatment
• Offers a cure rate of 95% or higher¹
• Few side effects and minimal follow-up testing

Important Considerations:

• Only available at specialized facilities licensed to handle radioactive materials
• Hospital stay ranges from 3 days to 4 weeks, depending on regulations
• Owners cannot visit during hospitalization
• After discharge, safety guidelines must be followed for about 2 weeks; this may include keeping your cat indoors, limiting close contact and safely disposing of waste

2. Antithyroid Medications

Antithyroid medication, such as methimazole or carbimazole, is a common and effective way to manage hyperthyroidism in cats. These cat thyroid medicines reduce the production of thyroid hormones by blocking an enzyme involved in hormone synthesis. This treatment is often used when other options, such as radioactive iodine therapy or surgery, are not suitable.

Key Benefits:

• Effective in managing thyroid hormone levels in most cats
• Noninvasive and available in multiple forms to suit your cat’s needs
• A good option for cats that are not candidates for more advanced treatments

Important Considerations:

• Must be given every day, often twice daily, for the rest of your cat’s life
• Does not cure the disease
• Requires regular veterinary checkups and blood tests to monitor hormone levels, kidney function and side effects
• Side effects of thyroid medicine for cats may occur in up to one in four cats¹ and can include vomiting, itching, liver problems and changes in blood cell counts
• The thyroid tumor may continue to grow and could become cancerous in rare cases

3. Surgical Thyroidectomy

Surgical removal of the thyroid gland, called a thyroidectomy, is another effective treatment for feline hyperthyroidism. It offers a rapid cure, especially when both glands are removed. Many general veterinary surgeons can perform the procedure, and thyroid hormone levels usually return to normal within 1-2 days.

Key Benefits:

• Provides a fast and often permanent cure
• Cure rate is over 90% when both glands are removed¹
• Does not require lifelong medication

Important Considerations:

• Requires general anesthesia
• Cats usually need to be stabilized with medication before surgery
• Hospitalization is needed during recovery
• Surgery is not reversible
• Some cats may have a change in their voice or purr after the procedure

4. Therapeutic Iodine-Restricted Diet

Feeding a therapeutic iodine-restricted diet is a noninvasive way to manage hyperthyroidism in cats. Diet is especially important in these cats because it helps reduce the production of thyroid hormones by limiting iodine. It does not involve medication, surgery or hospitalization and is considered safe for cats with kidney disease.

Key Benefits:

• Noninvasive and easy to administer
• No daily medication or procedures required
• About 82% of cats respond well to the diet¹
• Safe for cats with kidney disease
• May be a good option for older cats who cannot tolerate other treatments

Important Considerations:

• For a cat with an overactive thyroid, diet is crucial; it must be fed exclusively for life with absolutely no other food, treats or table scraps
• Exposure to outside food or prey will interfere with effectiveness
• Regular veterinary monitoring is needed to track progress
• Can be difficult in multi-cat households or for cats with other dietary needs
• Not suitable for cats on flavored medications or iodine-containing supplements
• Indoor-outdoor cats may not be good candidates due to access to outside food sources

Choosing the Right Treatment for Hyperthyroidism in Cats

Your veterinarian can help choose the best treatment based on your cat’s age, health and lifestyle. Radioactive iodine therapy and surgery are often preferred for younger, healthy cats, while medication or a special diet may be better for older cats or those with other conditions. Sometimes, medication is used first to stabilize hormone levels before a permanent treatment is chosen. Regular monitoring is important with any option.

Talk to your veterinarian to discuss the pros and cons of each approach and decide what’s best for your cat’s long-term health.

For more expert tips on hyperthyroidism in cats, explore the causes and diagnosis.

Reference

1. Carney HC, Ward CR, Bailey SJ, et al. 2016 AAFP guidelines for the management of feline hyperthyroidism. J Feline Med Surg. 2016;18(5):400-416.