Comparing radioactive iodine and medical management for hyperthyroidism

Comparing radioactive iodine and medical management for hyperthyroidism

Various treatment options exist for treatment of hyperthyroidism in cats. The following table will help provide you with information comparing medical therapy (methimazole) the different treatment options.

Radioactive Iodine I131

  • Single cost treatment
  • No side effects
  • Single oral capsule. Small number of patients may require a second treatment.
  • Routine follow up care
  • Post-treatment hypothyroidism rare
  • Destruction of thyroid tissue regardless of size or location
  • Destruction of cancerous thyroid tissue
  • Changes to intrakidney pressure and protein loss through the kidneys likely to resolve
  • Stops progression of kidney disease associated with hyperthyroidism
  • Longest survival

Medical therapy e.g. methimazole

  • Over time often more expensive than surgery or radioiodine
  • Side effects common such as itchy skin, vomiting or problems with changes in blood cells
  • Life long daily or twice daily treatment
  • Frequent monitoring required as necessary dosage changes over time
  • Induction of hypothyroidism common and frequent monitoring required
  • Thyroid cancer continues to grow requiring regular changes to medication
  • Thyroid tumour can undergo malignant transformation and invade or spread during long term medical management
  • Unless extremely tightly controlled intrakidney pressures and protein loss through the kidneys will progress and may cause kidney failure
  • Unless perfectly controlled, persistent changes in intrakidney pressures may cause progression of kidney failure
  • Shortest survival


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