Radioactive Iodine: Best Treatment for Hyperthyroidism in Cats

Hyperthyroidism, the over-production of thyroid hormone, is a widespread condition primarily affecting older cats. The reasons for its increasing prevalence remain unclear, but the symptoms are well recognised, including weight loss, increased appetite and heart rate, and a poor coat condition. Left untreated, hyperthyroidism can lead to severe and potentially life-threatening complications. Once diagnosed through a blood test, a vet will discuss suitable treatment options.

Treating Hyperthyroidism in Cats

There are several treatments for managing hyperthyroidism in cats, each with benefits and considerations.

Dietary Management: A prescription low-iodine diet can reduce thyroid hormone production by limiting iodine intake. However, this diet must be fed exclusively, which can be challenging, especially in multi-cat households, as cats may reject the diet.

Medication: Anti-thyroid drugs are commonly prescribed to inhibit excess thyroid hormone production. These require daily administration for life, along with regular blood tests to ensure appropriate dosing. Yet some cats resist taking medication, and alternative administration such as ear gels can be tricky. Side effects are also a concern, ranging from mild to severe, and, importantly, the underlying thyroid tumour remains untreated, potentially growing and posing further risks.

Surgery: Thyroidectomy, or surgical removal of the affected thyroid tissue, can cure hyperthyroidism. Nevertheless, it is not suitable for all cats, especially those with disease in both thyroid glands or tumours in inaccessible locations such as the chest. Surgery carries risks such as damage to the parathyroid glands involved in calcium regulation, and some cases may be inoperable.

Radioactive Iodine: Recognised as the gold standard treatment for feline hyperthyroidism, radioactive iodine (I-131) offers a near-complete cure with minimal side effects. This treatment delivers a carefully measured radioactive iodine dose that selectively destroys the abnormal thyroid tissue, preserving healthy thyroid and parathyroid glands. It achieves a cure rate in approximately 95% of cases, sometimes cited as high as 99%.

How Radioactive Iodine Treatment Works

Radioactive iodine is administered as a single injection under the skin, frequently in the scruff of the neck. The iodine preferentially accumulates in the hyperactive thyroid tumour cells, which are then destroyed over days to weeks. Cats usually respond within a few weeks, though full effects may take several months. Occasionally, a second dose may be needed if hyperthyroidism persists.

Hospital Stay and Care Requirements

Due to the radioactive nature of the treatment, cats must be treated at specialist centres and remain hospitalised for one to three weeks to limit radiation exposure to owners and the public. During hospitalisation, cats are housed individually with access to food and water and can receive limited contact with protective measures in place. After release, cats remain slightly radioactive for up to six weeks, requiring confinement in a safe area at home, strict handling precautions, and careful disposal of waste until the radioactivity declines to a safe level.

Advantages of Radioactive Iodine Therapy

• High success rate with complete cure in most cases
• Minimal side effects and preservation of healthy thyroid tissue
• Non-invasive compared to surgery; no general anaesthetic required
• Long-term solution preventing recurrence of disease
• Potentially cost-effective considering lifelong medication costs

Considerations and Potential Disadvantages

• Higher upfront cost compared to medication or diet
• Necessity of hospitalisation and temporary separation from owners
• Post-treatment isolation and radioactivity precautions at home
• Rare cases of hypothyroidism may require thyroid hormone supplementation

Conclusion

Radioactive iodine therapy is widely considered the most effective and safest treatment for hyperthyroidism in cats, particularly in those otherwise in good health. Its ability to provide a permanent cure with minimal risks makes it the preferred option in the UK veterinary community. While the temporary inconvenience of hospital stay and post-treatment care exists, most cat owners report excellent outcomes and satisfaction with this treatment choice.

If your cat has been diagnosed with hyperthyroidism, consult a trusted veterinary professional about whether radioactive iodine therapy is suitable. Responsible and well-informed treatment decisions can significantly improve your cat's quality of life and longevity.