[Reference values for the concentrations of triiodothyronine, thyroxine and thyrotropin in the blood serum of euthyroid children. Method: luminescence-enhanced enzyme immunoassay].

Concentrations of triiodothyronine, thyroxine and thyrotropin were determined using the luminescence enhanced enzyme immunoassay method in blood serum of 343 (male = 197, female = 146) euthyroid children. Beyond the newborn age no significant difference was found for the thyrotropin concentration. Compilation of the values resulted in a physiological thyrotropin concentration of 1.73 +/- 0.81 (1s) microU/ml for infants, children and juveniles. In opposition to these results the thyroxine and triiodothyronine concentration showed an age-specific dependence. The thyroxine and triiodothyronine concentrations (means +/- 1s) decreased continuously from the infant age (TT4: 182.1 +/- 37.7 ng/ml, 234.9 +/- 48.6 nmol/l, TT3: 1.77 +/- 0.57 ng/ml, 2.73 +/- 0.88 nmol/l) to the juvenile age (TT4: 77.9 +/- 14.3 ng/ml, 100.5 +/- 18.4 nmol/l, TT3: 1.25 +/- 0.31 ng/ml, 1.93 +/- 0.48 nmol/l). The luminescence enhanced enzyme immunoassay technique is suitable for use in the routine thyroid laboratory.