A Cure for Feline Hyperthyroidism

Safe, effective treatment to help your cat feel like themselves again

Hyperthyroidism is one of the most common conditions affecting older cats—but it’s also one of the few we can often treat successfully with a single therapy.

This condition is caused by a tumor in the thyroid gland (more than 97% are benign) that produces too much thyroid hormone. This creates an overactive metabolism that can affect your cat’s weight, heart, kidneys, and overall behavior.

Common signs you may notice:

• Weight loss despite a strong or increased appetite
• Increased thirst and urination
• Vomiting or diarrhea
• Changes in coat quality (hair loss or a dull coat)
• Restlessness, anxiety, or increased vocalization
• Elevated heart rate or heart murmur

Left untreated, hyperthyroidism can lead to serious complications, including heart disease and organ damage. Early diagnosis and treatment make a meaningful difference.

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Understanding your treatment options

There are several ways to manage hyperthyroidism. The right approach depends on your cat’s health and your long-term goals.

I‑131 Therapy (Radioactive Iodine) — the gold standard

I‑131 therapy is considered the most effective and least invasive treatment available.

• A single injection treats the disease at its source
• Overactive thyroid tissue is selectively destroyed
• Healthy thyroid tissue is typically preserved
• Most cats return to normal thyroid function
• No daily medications required
• Proven longer lifespan when compared to Methimazole therapy (4 years vs. 2 years)

This approach treats the underlying cause, not just the symptoms. I-131 therapy requires your cat(s) be medically boarded at VICSD for the week (99% of cats are treated on Monday and discharged on Friday).

Learn about I-131 therapy:

• I-131 abstract
• Lecture
• Videos

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Daily medication (Methimazole / Tapazole/ Felimazole)

Medication can help control hormone levels, but:

• It does not cure the disease
• Requires lifelong, daily dosing
• Needs regular bloodwork monitoring
• May cause side effects such as vomiting or changes in blood counts
• Has been shown to be associated with a shorter lifespan compared to I-131 therapy (2 years vs. 4 years)

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Prescription iodine-restricted diet

Dietary therapy may help in some cases, but:

• Requires strict adherence (no other food or treats)
• Is not a cure
• May not be practical for all cats or households

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Why many veterinarians recommend I‑131 therapy

I‑131 is the only treatment that can eliminate the abnormal thyroid tissue responsible for hyperthyroidism.

It is widely used because it:

• Avoids surgery
• Requires minimal intervention
• Has a high success rate
• Reduces long-term management burden

Veterinary radiologists have long emphasized the value of advanced imaging and targeted therapies in improving diagnostic accuracy and outcomes. Educational materials authored by board-certified radiologist Dr. Seth Wallack highlight how modern imaging and treatment techniques—including CT and nuclear medicine—allow for more precise, effective care in veterinary patients.

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What to expect with I‑131 therapy

Treatment day

Your cat receives a single injection of radioactive iodine. The treatment is painless and does not require surgery.

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Hospital stay

Because of strict safety regulations, your cat will stay with us for a minimum of 5 days. This allows radiation levels to safely decrease before returning home.

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Monitoring and communication

While your cat is with us:

• We monitor eating, drinking, and behavior multiple times daily
• We track litterbox habits and overall health
• We provide regular updates so you always know how your cat is doing

You can also:

• Visit during business hours and see your cat through our viewing window
• Check in remotely through our I‑131 Cat WebCam

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Expected outcomes

• Approximately 98% of cats are successfully treated with I‑131
• A small number may need a second treatment
• Some cats develop low thyroid levels afterward, which can be easily managed

Most cats gradually return to a more normal weight, energy level, and behavior in the weeks following treatment.

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Why choose VICSD for I‑131 therapy?

We are proud to be a leader in the diagnosis and treatment of feline hyperthyroidism.

What sets us apart:

• Extensive experience with hyperthyroid cats
• Advanced imaging and diagnostic capabilities
• Personalized care for every patient
• Close communication with your primary veterinarian
• A 98% success rate in treatment outcomes

Our approach is grounded in advanced radiology expertise and a commitment to applying the latest diagnostic and therapeutic techniques in veterinary medicine.

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Our comprehensive care approach

Every I‑131 treatment includes:

• Full consultation and physical exam
• Imaging review
• Thyroid scan to confirm diagnosis and rule out rare aggressive tumors
• Cardiac ultrasound (to evaluate heart health)
• Treatment and hospitalization
• Post-treatment monitoring and follow-up

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Why careful screening matters

Hyperthyroidism can sometimes mask other underlying conditions—especially kidney disease.

To ensure safety, we may recommend:

• A trial of medication (Methimazole) before treatment
• Additional imaging or testing if needed

This helps ensure we are treating the patients safely and effectively.

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After your cat returns home

Once home:

• Your cat may take time to regain weight and strength
• Follow-up bloodwork is typically recommended at:
  • 1 month
  • 3 months
  • 6 months
  • 12 months

We work closely with your veterinarian to monitor recovery and long-term health.

You will also receive clear instructions to ensure safe care for your family and your cat during the short post-treatment period.

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Helping your cat live a longer, healthier life

Hyperthyroidism can be a serious diagnosis—but it is also one of the most treatable.

Our goal is simple:
Deliver safe, effective care that restores your cat’s health—and your peace of mind.