The objective of this study was to describe the findings in dogs with exogenous thyrotoxicosis attributable to the consumption of commercially available dog foods or treats containing high concentrations of thyroid hormone.

Medical records were searched to identify dogs with exogenous thyrotoxicosis attributable to dietary intake. One case found and subsequent cases were identified prospectively, for a total of 14 dogs studied. Serum thyroid hormone concentrations were evaluated before and after feeding meat-based products suspected to contain excessive thyroid hormone was discontinued. Scintigraphy was performed to evaluate thyroid tissue in 13 of 14 dogs before and one of 13 dogs after discontinuation of suspect foods or treats. Seven samples of five commercially available products fed to six affected dogs were analyzed for thyroxine concentration; results were subjectively compared with findings for 10 other commercial foods and six beef muscle or liver samples.

Total serum thyroxine concentrations were high in all dogs at initial evaluation; scintigraphy revealed subjectively decreased thyroid gland radionuclide in 13 of 13 dogs examined. At ≥ four weeks after feeding of suspect food or treats was discontinued, total thyroxine concentrations were within the reference range for all dogs and signs associated with thyrotoxicosis, if present, had resolved. Results indicated that thyrotoxicosis can occur secondary to consumption of meat-based products presumably contaminated by thyroid tissue, and can be reversed by identification and elimination of suspect products from the diet.

Source:  Michael R. Broome, DVM, MS, et al., 2015. Exogenous thyrotoxicosis in dogs attributable to consumption of all-meat commercial dog food or treats containing excessive thyroid hormone: 14 cases (2008–2013). JAVMAonline, January 2015. doi: 10.2460/javma.246.1.105.