Serum total thyroxine, total triiodothyronine, free thyroxine, and thyrotropin concentrations in dogs with nonthyroidal disease

Results indicate that serum total T4, free T4, and total T3 concentrations may be low (ie, in the hypothyroid range) in dogs with moderate to severe nonthyroidal disease. Serum TSH concentrations are more likely to remain within the reference range in sick dogs.