Society of Veterinary Nuclear Medicine

16-year-old castrated male Domestic Long Hair

Chronic history of hyperthyroidism.

Additional History

  • Managed homeopathically and recently has been declining clinically as the cat became anorexic.

Physical Exam

  • Emaciated, marked goiter and fleas.


  • Total T4 – 17 mcg/gL, PCV 25%, Reticulocytes 0.7%.

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    Thoracic radiograph
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    Thoracic Radiograph
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Abdominal ultrasound

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    Pre-treatment technetium scan
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    Post-treatment technetium scan
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Cardiomegaly without congestive heart failure.

Eccentric left ventricular hypertrophy and left atrial enlargement.

  • Small volume of peritoneal effusion (modified transudate)
  • Single, small hyperechoic hepatic mass with internal cystic regions (probably biliary cystadenoma)

Multiple, irregularly marginated areas of increased radionuclide uptake involving the ventral cervical and thoracic regions typical for differentiated thyroid carcinoma.

  • Thyroid carcinoma causing thyrotoxicosis
  • Incidental biliary cystadenoma
  • Anemia of chronic disease
  • Mild peritoneal effusion

Responded well to methimazole and high dose radioiodine (30 mCi). Had an excellent clinical response with marked weight gain, resolved anemia and resolved peritoneal effusion.

  • Peterson M.E. and Broome M.R. Hyperthyroid Cats on Long-Term Medical Treatment Show a Progressive Increase in the Prevalence of Large Thyroid Tumors, Intrathoracic Thyroid Masses and Suspected Thyroid Carcinoma. in Conference Proceedings ECVIM. 2012. Maastricht, Netherlands.
  • Hibbert A., Gruffydd-Jones T., Barrett E.L., et al., Feline Thyroid Carcinoma: Diagnosis and Response to High-Dose Radioactive Iodine Treatment. J Feline Med Surg, 2009. 11(2): p. 116-24.
  • Broome M.R. Hyperthyroid Summit: Therapy of Hyperthyroid Cats with Large Thyroid Masses. in Conference Proceedings New York State Veterinary Conference. 2012. New York.