Effect of thyroid volume on radioiodine therapy outcome in hyperthyroid cats.

Abstract

Radioiodine therapy is commonly used in hyperthyroid cats and has a high success rate, ranging from 85-95%. As in humans, thyroid volume has been reported to influence radioiodine therapy outcome in hyperthyroid cats. The purpose of this study was to relate total thyroid volume, calculated by a newly constructed formula for feline patients (0.438 × length × width²), to the outcome of radioiodine therapy. To search for a correlation between total thyroid volume and therapy outcome, 167 hyperthyroid cats were included. Patients were categorised according to the administered radioiodine dose and therapy outcome. Our analysis did not show a significant relationship between an increasing total thyroid volume and the odds for a final low total thyroxine concentration (TT4; P = 0.3930) or a final hyperthyroid outcome (P = 0.0901). A significant relationship was found for an increase in the odds for a final low TT4 outcome with an increase in the number of foci detected on the pertechnetate thyroid scan (P = 0.0238). This was not true for a final hyperthyroid outcome (P = 0.7435). The number of detected foci was also significantly associated with the total thyroid volume (P = 0.0006). Findings indicated that the presence of multiple affected foci influences therapy outcome towards a low TT4 outcome. Bilateral hyperthyroidism and its potential effect on a final low TT4 outcome should therefore be addressed when informing owners of the possible outcomes of radioiodine therapy for their cat.

• Authors: Veerle Volckaert, Eva Vandermeulen, André Dobbeleir, Luc Duchateau, Jimmy H Saunders, Kathelijne Peremans
• Journal: Journal of feline medicine and surgery (J Feline Med Surg) Vol. 18 Issue 2 Pg. 144-9 (Feb 2016) ISSN: 1532-2750 [Electronic] England
• PMID: 25769623 (Publication Type: Journal Article)
• Copyright: © ISFM and AAFP 2015.

Chemical References

• Antithyroid Agents
• Iodine Radioisotopes
• Radiopharmaceuticals
• Iodine

Topics

• Animals
• Antithyroid Agents (therapeutic use)
• Cat Diseases (drug therapy, radiotherapy)
• Cats
• Hyperthyroidism (radiotherapy, veterinary)
• Iodine (therapeutic use)
• Iodine Radioisotopes (therapeutic use)
• Radiopharmaceuticals (therapeutic use)
• Thyroid Gland (drug effects)
• Treatment Outcome