Reassessment of the daily dose of oral thyroxine for replacement therapy in hypothyroid children.

The optimal daily requirement of sodium L-thyroxine for replacement therapy of hypothyroidism was evaluated in 11 hypothyroid children ranging from one to 14 years of age. The "optimal" dose of L-T4, defined as the minimal daily dose necessary to suppress the serum concentration of TSH to normal, was determined in each patient and individual growth rates were assessed for periods up to 12 months during the time this dose was being administered. The mean "optimal" dose of L-T4 was 3.78 +/- 0.6 mug/kg or 104.6 +/- 5.2 mug/m2. This dose was considerably lower than the doses of L-T4 generally recommended. All patients appeared clinically euthyroid, and their serum concentrations of T3 and T4 as well as their height velocities remained within the normal range while the "optimal" dose of L-T4 was being adminstered.