To explore the reference intervals for thyroid function test indicators of free triiodothyronine (FT₃), free thyroxine (FT₄), and thyroid stimulating hormone (TSH) in children aged 1~6 in Guangzhou.

A total of 240 physical examination specimens of children aged 1~6 in Guangzhou were selected, and the levels of the indexes of serum thyroid function (FT₃, FT₄, TSH) were uniformly measured by using the Abbott Chemiluminescence Immunoassay Analyzer, compared the results of thyroid function index with healthy adults, and establishing reference intervals for thyroid function indicators FT₃, FT₄, and TSH in children aged 1~6 in Guangzhou.

The reference intervals of thyroid function indicators FT₃, FT₄, and TSH for children aged 1~3 and 4~6 groups in Guangzhou were 5.56 (4.46~6.74) pmol/L, 14.17 (11.67~16.98) pmol/L, 1.88 (0.76~3.99) μIU/mL, and 5.64 (4.70~6.63) pmol/L, 14.18 (11.99~16.65) pmol/L, 1.89 (0.60~3.90) μIU/mL, that are quite different from the reference interval provided by the kits. The levels of FT₃ and TSH in children between the ages of 1~3 and 4~6 groups were higher than those in the adult control group (P＜0.05). There was no significant difference in the level of FT₄ between the two groups of children and the adult control (P＞0.05). Comparison of FT₃, FT₄, and TSH levels between the two groups were not statistically significant (P＞0.05). The FT₃ and TSH levels of different sexes in the healthy adult control group were compared. The FT₃ level of male was higher than the female, and the TSH level of male was lower than that of women (P＜0.05). There was no significant difference in FT₄ levels between healthy adults of different genders (P＞0.05).

Initially established the normal reference intervals of thyroid function indicators FT₃, FT₄, and TSH for children aged 1~6 in Guangzhou in this laboratory, so as to provide a reference basis for better screening of thyroid-related diseases in children.