Evaluation of sodium L-thyroxine (T4) requirement in replacement therapy of hypothyroidism.

Sodium-L-thyroxine (T4) was utilized in the treatment of 15 pediatric patients with hypothyroidism. Adequacy of replacement therapy was confirmed by clinical evaluation in conjunction with determination of serum thyroxine, tri-odothyronine, and thyrotropin concentrations. Daily dose of thyroxine capable of including clinical and biochemical euthyroidism ranged from 2.5 to 5 mug/kg of body weight with a mean of 3.5 +/- 0.3 mug in the 4- to 17-year-old age group. Two infants with congenital hypothyroidism diagnosese observations imply that physiologic requirements of thyroxine are distinctly lower than previously recommended dosages. Further studies to establish more precise therapeutic guidelines are needed.