Guptill L, Scott-Moncrieff CR, Janovitz EB, et al.
Summary: Seven cats with thyroid carcinomas that had previously undergone surgical removal of neoplastic tissue were treated with 30 mCi of radioactive iodine (I-131). Six of the cats had clinical signs hyperthyroidism; 1 did not. There were no complications associated with I3ll treatment, and clinical signs resolved in all cats. Technetium scans of 4 cats made after treatment did not have evidence of isotope uptake. In the remaining 3 cats, small areas of isotope uptake, the intensity of which was equal to or less than the intensity of uptake in the salivary glands, were seen. All 7 cats became hypothyroid after treatment; 4 required L-thyroxine supplementation. One cat was alive 33 months after treatment. The other 6 cats were euthanatized because of unrelated diseases 10 to 41 months after treatment. Thyroid scintigraphy was performed by injecting 2 to 3 mCi of sodium pertechnetate, IV, and imaging the cat’s neck and thorax with a gamma camera 30 minutes later. Cardiac ultrasonography was performed in 5 cats.