title: 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.affiliation: Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium veerle.volckaert@ugent.be.
authors.forename: Veerle
authors.initials: V
authors.lastname: Volckaert
authors.affiliation: Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium.
authors.forename: Eva
authors.initials: E
authors.lastname: Vandermeulen
authors.affiliation: Department of Nuclear Medicine, Ghent University Hospital, Ghent, Belgium.
authors.forename: André
authors.initials: A
authors.lastname: Dobbeleir
authors.affiliation: Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium.
authors.forename: Luc
authors.initials: L
authors.lastname: Duchateau
authors.affiliation: Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium.
authors.forename: Jimmy H
authors.initials: JH
authors.lastname: Saunders
authors.affiliation: Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium.
authors.forename: Kathelijne
authors.initials: K
authors.lastname: Peremans
mesh_terms: D000818:Animals; D013956:Antithyroid Agents / Q000627:therapeutic use; D002371:Cat Diseases / Q000188:drug therapy* / Q000532:radiotherapy*; D002415:Cats; D006980:Hyperthyroidism / Q000532:radiotherapy / Q000662:veterinary*; D007455:Iodine / Q000627:therapeutic use*; D007457:Iodine Radioisotopes / Q000627:therapeutic use*; D019275:Radiopharmaceuticals / Q000627:therapeutic use; D013961:Thyroid Gland / Q000187:drug effects; D016896:Treatment Outcome
chemical_list: D013956:Antithyroid Agents; D007457:Iodine Radioisotopes; D019275:Radiopharmaceuticals; D007455:Iodine