Radio-iodine treatment of hyperthyroid cats

Area of Science:

• Veterinary Internal Medicine
• Endocrinology
• Nuclear Medicine

Background:

• Hyperthyroidism is a common endocrine disorder in older cats.
• Radioactive iodine (131I) therapy offers a targeted treatment for feline hyperthyroidism.
• Accurate dosimetry is crucial for successful 131I treatment outcomes.

Purpose of the Study:

• To evaluate the efficacy and safety of radioactive iodine (131I) therapy in elderly cats with hyperthyroidism.
• To determine the success rate of 131I treatment based on individualized dosage.
• To assess the incidence of hypothyroidism and persistent hyperthyroidism post-treatment.

Main Methods:

• Thirty-two elderly domestic shorthaired cats with hyperthyroidism were treated with a calculated dose of radioactive iodine (131I).
• Dosing ranged from 39 mBq to 134 mBq, determined by clinical signs, thyroid gland size, and serum thyroxine levels.
• Treatment outcomes were monitored by assessing thyroid hormone levels and clinical status.

Main Results:

• Twenty-eight of thirty-two cats (87.5%) became euthyroid after a single 131I treatment.
• One cat developed hypothyroidism, and three cats remained hyperthyroid; two of these were successfully re-treated.
• Five cats died from concurrent diseases within one year, unrelated to the 131I therapy.

Conclusions:

• Individualized dosing of radioactive iodine (131I) is an effective and safe treatment for hyperthyroidism in elderly cats.
• The treatment protocol resulted in a high success rate, with most cats achieving a euthyroid state.
• Radioiodine therapy provides a viable long-term solution for feline hyperthyroidism, improving quality of life.