The most common clinical signs are weight loss, increased appetite, and increased thirst and urination. It may also cause vomiting, diarrhoea, hyperactivity and a matted or greasy coat.

Diagnosis involves a physical exam, palpating the neck, and a blood-chemistry panel plus thyroid-hormone level test.

There are four treatment options: medication, diet (Hill’s Y/D), surgical thyroidectomy, or radioactive-iodine therapy, which is curative in approximately 95% of cases.