Free triiodothyronine concentration in serum of 1050 euthyroid children is inversely related to their age.
Free triiodothyronine was assayed in serum of 1050 euthyroid children with the Amerlex-MAB method. We studied 50 samples for each year of age, from < 1 to 20, and no child had more than one sample taken. A gradient of values was observed, increasing by 31% from 5.04 pmol/L as the mean of 20-year-old patients to 6.59 pmol/L in the serum of children younger than 1 year. For practical reasons the lower normal limit was proposed to remain at 3.4 pmol/L for all patients; the higher limit can be set at 8.3 (0 to 3 years), 7.8 (4 to 7 years), 7.1 (8 to 11 years), 6.8 (12 to 15 years), and 6.7 (16 to 19 years). Preferably, the regression line of the mean + 2 SD can be used, resulting in a high normal limit of 8.3 pmol/L at birth to 6.3 pmol/L at 20 years, decreasing by 0.1 pmol/L per year.
Verheecke
P
P
Centraal Laboratorium Hasselt, Hasselt, Belgium. paul.verheecke@club.innet.be
D000293:Adolescent; D000328:Adult; D000375:Aging / Q000097:blood*; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D012016:Reference Values; D013961:Thyroid Gland / Q000502:physiology*; D014284:Triiodothyronine / Q000097:blood*
D014284:Triiodothyronine