Serum TSH should be undetectable in patients with active hyperthyroidism; serum total and free T₄ and T₃ may be measured and are usually elevated. Although there may be different approaches based on background and clinical practice, most patients with suspected Graves disease should have free T₄, total triiodothyronine (TT₃), and TSH determined initially to help confirm the diagnosis. When patients with known Graves disease are observed, usually free T₄ and TT₃ are determined, and occasionally TSH may be useful. Evaluation of TT₃ levels should be routine, but may be especially useful when the clinical signs or symptoms are marked and seemingly disproportionate to the free T₄ elevation.34,35 T₃ toxicosis, a condition of clinical thyrotoxicosis with a normal serum T₄ level but an elevated TT₃ level, is relatively unusual; it is more likely to occur in patients with an autonomous nodule, early Graves disease, or recurrent disease. To develop tests that would not be influenced by binding proteins, investigators have developed free T₄ and free T₃ measurements that are sensitive and applicable to clinical use.35,36,37 and 38 Free T₄ should replace the more traditional total T₄ and resin T₃ uptake tests given that it is not influenced by alterations in binding proteins and because it is now widely available. However, free T₃ is not yet readily available commercially with a rapid turnaround time; therefore, it is still appropriate to obtain a TT₃ level, although it must be remembered that TT₃ levels are increased when there are elevations of T₄-binding globulin (e.g., pregnancy, estrogen).

Serum thyroglobulin levels and antithyroglobulin or antimicrosomal antibodies need not be measured routinely in a patient with Graves disease.