Evaluation of dietary and environmental risk factors for hyperthyroidism in cats.

To identify dietary and environmental risk factors for hyperthyroidism in cats. Case-control study. 100 cats with hyperthyroidism and 163 control cats. Medical records were examined, and owners completed a mailed questionnaire. Data collected included information regarding demographic variables, environmental exposures, and diet, including preferred flavors of canned cat food. Case cats were significantly less likely to have been born recently than control cats. Housing; exposure to fertilizers, herbicides, or plant pesticides; regular use of flea products; and presence of a smoker in the home were not significantly associated with an increased risk of disease, but cats that preferred fish or liver and giblets flavors of canned cat food had an increased risk. Results suggest that cats that prefer to eat certain flavors of canned cat food may have a significantly increased risk of hyperthyroidism.