How effective is 131I therapy?
The first dose of 131I will cure hyperthyroidism in 97-98% of hyperthyroid cats. 70% of cats have normal thyroid levels (T4) within one week of 131I therapy. 90% have normal T4 levels by one month and 97% have normal T4 levels by three months. There are a few cats in whom it can take as long as 6 months for resolution of hyperthyroidism. If a second dose of 131I is required within the first six months to cure your cat, there is no charge for this procedure provided the follow up labwork is performed in a timely manner. Following successful 131I therapy, only 0.3% (1 in 300) cats will become hyperthyroid again in their lifetime.
