I would have done a full panel. You can have normal T4 but the conversion to T3 (the active form of thyroid hormone) can be abnormal. Another thing that can be abnormal is the autoantibodies (which means that the thyroid gland is having an autoimmune problem and destroying itself). Just checking T4 works as a screening tool in dogs, once they’ve been properly diagnosed, to say that their medication is at the right level. T4 alone is a good diagnostic tool for feline hyperthyroidism. Dogs can have normal T4 levels but have thyroid dysfunction. Dogs can have low T4 levels but have normal thyroid function. It takes a full panel (T4, T3, fT4, fT3, TGAA) to correctly diagnose canine thyroid function.