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SAGE Veterinary Centers

Radioactive Iodine Therapy (I131) for Hyperthyroid Cats

Hyperthyroidism is the most common hormonal disease in cats other than diabetes. This disease is caused by high circulating amounts of thyroid hormone.

This service is offered in our Redwood City location.


This therapy used to treat Hyperthyroidism. the second most common hormonal disease in cats after diabetes.

Treatment options include methimazole, radioactive iodine (I131) and surgery. Surgery is rarely recommended unless a malignant thyroid tumor is suspected.

Methimazole is an oral or transdermal medication that can be used to treat hyperthyroidism but it is only a mechanism of controlling the disease rather than curing it. Methimazole is a good option for treatment but has a higher likelihood of side-effects and requires twice daily administration. Routine monitoring will be required for life because often the dose needs to be escalated. If the thyroid levels are not well controlled, then the cat is more likely to have chronic kidney effects.

Radioactive iodine (I131) is considered to be the treatment of choice for hyperthyroidism because it cures the disease rather than just managing it. It is a one-time subcutaneous injection and has no side-effects. There is much less monitoring required long-term. Overall, this treatment is less expense than methimazole over the lifetime of the cat and it has also been shown to have the longest survival rates.

For more information on our iodine therapy services, please view our brochure here >


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