About feline hyperthyroidism

Feline hyperthyroidism is an endocrine disorder caused by a "benign goiter" of one or both thyroid glands that causes an elevation of thyroid hormone levels. The disorder commonly affects older cats.


Cats suffering from feline hyperthyroidism may exhibit the following symptoms:

  • eating, drinking and urinating more than normal
  • weight loss
  • hyperactivity
  • suffering coat-quality issues
  • rapid toenail growth
  • elevated heart rate and other clinical signs

Radioactive iodine therapy treatment

Radioactive iodine therapy is an extremely effective treatment for treating feline hyperthyroidism. Candidates for the radioactive iodine therapy should be relatively healthy cats that have been off their feline hyperthyroid medications for at least two weeks prior to treatment. The treatment protocol is as follows:

  • Upon admission, patients are provided with a comprehensive health evaluation and a thyroid scan to ascertain the extent of the problem and to develop a therapeutic approach.
  • A low dosage of radioactive iodine is administered to the patient through a single subcutaneous injection.
  • The agent is accumulated and concentrated in the abnormal parts of the thyroid glands.The iodine destroys the diseased tissue, while healthy thyroid tissues are not affected.
  • Once the agent is injected, the patient must be kept in isolation for three or four days while the radioactive agent is cleared from the body.

Scheduling an appointment for radioactive iodine therapy

To schedule an appointment for this service at the VTH, please consult with your primary care veterinarian to arrange a referral to our hospital for your feline companion.

Steps for the primary care veterinarian:

  • Call the Small Animal Hospital at 540-231-4621 to arrange the referral.
  • Complete the VTH Referral Form.
  • The form may be submitted electronically, faxed to 540-231-9354, or given to the client to deliver at the scheduled appointment time.

Special thanks

We are especially grateful to the late Joanne O'Brien, whose generous gift enabled the renovation of our animal holding and treatment facilities to support the operation of the radioactive iodine therapy service.