Hyperthyroldism with Normal Values for Total

We assessed the frequency and clinical background of normal concentrations of serum total thyroxin (T4) found among 84 hyperthyroid patients out of 633 consecutive patients evaluated for suspected hyperthyroidism. Patients were categorized as having hyperthyroidism if they had hyperthyroid symptoms and signs, had a serum thyrotropin (TSH) 0.1 milli-int. unitJL as measured by immuneradiometric assay (Farmos Diagnostica, Turku, Finland), and needed treatment. Serum total T4 determined with a radioimmunoassay (Farmos Diagnostica; reference interval 70-150 mnoIJL) was normal in 17 hyperthyroid subjects among 68 patients (25%) without previous thyroid history (Figure 1). Normal T4 values were common in patients with nodular goiter (34.8%, eight of 23), but seldom found in cases of Graves’ hyperthyroidism (10.5%, four of 38). Moreover, normal T4 values were more common in relapsed clinical disease than in newly diagnosed cases (chi-square = 8.18, P <0.01). Results for all 84 hyperthyroid patients were as follows: