Survival times for cats with hyperthyroidism treated with iodine 131, methimazole, or both: 167 cases (1996-2003).
OBJECTIVE
To compare survival times for cats with hyperthyroidism treated with iodine 131, methimazole, or both and identify factors associated with survival time.


METHODS
Retrospective case series.


METHODS
167 cats.


METHODS
Medical records of cats in which hyperthyroidism had been confirmed on the basis of high serum thyroxine concentration, results of thyroid scintigraphy, or both were reviewed.


RESULTS
55 (33%) cats were treated with 131I alone, 65 (39%) were treated with methimazole followed by 131I, and 47 (28%) were treated with methimazole alone. Twenty-four of 166 (14%) cats had preexisting renal disease, and 115 (69%) had preexisting hepatic disease. Age was positively correlated (r = 0.4) with survival time, with older cats more likely to live longer. Cats with preexisting renal disease had significantly shorter survival times than did cats without preexisting renal disease. When cats with preexisting renal disease were excluded, median survival time for cats treated with methimazole alone (2.0 years; interquartile range [IQR], 1 to 3.9 years) was significantly shorter than median survival time for cats treated with 131I alone (4.0 years; IQR, 3.0 to 4.8 years) or methimazole followed by 131I (5.3 years; IQR, 2.2 to 6.5 years).


CONCLUSIONS
Results suggest that age, preexisting renal disease, and treatment type were associated with survival time in cats undergoing medical treatment of hyperthyroidism.
Milner
Rowan J
RJ
Department of Small Animal Clinical Sciences, College of Veterinary Medicine, University of Florida, Gainesville, FL 32610-0126, USA.
Channell
Carla D
CD
Levy
Julie K
JK
Schaer
Michael
M
D000367:Age Factors; D000818:Animals; D013956:Antithyroid Agents / Q000627:therapeutic use*; D002371:Cat Diseases / Q000188:drug therapy*; D002415:Cats; D004359:Drug Therapy, Combination; D005260:Female; D006980:Hyperthyroidism / Q000188:drug therapy / Q000662:veterinary*; D007457:Iodine Radioisotopes / Q000627:therapeutic use*; D007674:Kidney Diseases / Q000150:complications / Q000662:veterinary; D008297:Male; D008713:Methimazole / Q000627:therapeutic use*; D012189:Retrospective Studies; D015996:Survival Rate; D016896:Treatment Outcome
D013956:Antithyroid Agents; D007457:Iodine Radioisotopes; D008713:Methimazole