Diet‐associated thyrotoxicosis in two dogs: Clinical, hormonal and imaging findings before and after dietary modification

ABSTRACT

Diet‐associated thyrotoxicosis is an uncommon disorder in dogs caused by ingestion of food contaminated with thyroid tissue, and it can mimic primary hyperthyroidism. We describe two dogs that presented with weight loss, restlessness, polyuria, polydipsia and markedly increased serum total thyroxine (T4) concentrations. In one dog, thyroid scintigraphy showed markedly decreased uptake of technetium‐99m pertechnetate, consistent with suppression of endogenous thyroid function by exogenous thyroid hormone. Dietary history identified likely sources of thyroid tissue exposure in both dogs: beef neck in one and chicken neck in the other. After both dogs were switched to balanced commercial diets, clinical signs resolved and serum T4 concentrations returned to normal. Follow‐up scintigraphy confirmed restoration of normal thyroid radionuclide uptake. These cases emphasise that diet‐associated thyrotoxicosis should be considered in dogs with increased serum T4 concentrations and that dietary history and thyroid scintigraphy help distinguish exogenous thyrotoxicosis from intrinsic hyperthyroidism.