Objective: The purpose of this study was to estimate the basal serum concentration reference values for total T3 (T3), total T4 (T4), free T4 (FT4), thyrotropin (TSH) and thyroglobulin (Tg) in healthy children of Zaragoza.
Patients and methods: Healthy children aged 0 to 14, with normal weight and height, living in the metropolitan area of Zaragoza (Spain) were the reference population of this transversal study. Basal serum concentrations of T3, T4 and FT4 were measured by radioimmunoassay and of TSH and Tg by immunoradiometric assay. Reference values and ranges were estimated according to the recommendations of the International Federation of Clinical Chemistry.
Results: Reference values have been classified according to age, sex and pubertal stage. There are differences in T3, T4, FT4 TSH and Tg concentrations during the prepubertal period according to age, but not to sex, and between the prepubertal period and puberty. Sex and Tanner stage influence T3 and T4 concentrations during puberty.
Conclusions: Since there are differences in T3, T4, FT4, TSH and Tg reference values according to age, sex, pubertal stage and immunoassays, it is necessary to establish reference values for every population and laboratory in accordance with these parameters.