Objective To analyze serum characteristics and determine the reference range for thyroid function among healthy 11～16 year-old teenagers in Xi'an in order to offer a theoretical basis for clinical diagnosis and therapy.Methods A sum of 1 378 healthy 11～16 year-old teenagers who met the inclusion criteria from the First Affiliated Hospital of the Air Force Medical University(Xijing Hospital)between January 2020 and December 2022 were selected as research subjects,including 628 males and 750 females.They were divided into three groups based on age:Group 1:11～＜13 year-olds(433 cases),Group 2:13～＜15 year-olds(425 cases),and Group 3:15～≤16 year-olds(520 cases).Differences in serum thyroid function indices among different genders and age groups were analyzed,the reference ranges for these indices were established,and 99 healthy 11-16 year-old teenagers who met the inclusion criteria were chosen for verification.Results There were no significant differences between different genders in thyroid stimulating hormone[TSH,2.56(1.80,3.63)μIU/ml vs 2.43(1.68,3.48)μIU/ml]and total thyroxine[TT4,97.84(85.34,111.00)nmol/L vs 98.20(87.16,111.23)nmol/L],the differences were statistically significant(Z=-1.881,-0.638,all P＞0.05).Meanwhile,the differences in free thyroxine[FT4,16.93(15.49,18.60)pmol/L vs 16.26(14.80,17.83)pmol/L],free triiodothyronine[FT3,6.21(5.66,6.80)pmol/L vs 5.59(4.98,6.19)pmol/L],and total triiodothyronine[TT3,2.24(1.96,2.55)nmol/L vs 2.04(1.78,2.34)nmol/L]between different genders were significant(Z=-5.368,-11.994,-6.417 all P＜0.01).The differences in thyroid function indices were significant among different age groups(Z=10.649～261.003,all P＜0.05).The reference ranges for thyroid function indices across different age groups and genders were established,in which thyroid function indicators were verified to be within the established reference range by 99 samples.Conclusion Teenage hormone secretion varies greatly,and the secretion of thyroid hormones is influenced by various factors.Thus,the diagnosis and treatment of teenage thyroid diseases cannot fully rely on the reference ranges provided by adults or manufacturers.This study established the reference range of the thyroid function indices of 11～16 year-old teenagers in Xi'an,offering clinical doctors'diagnosis and treatment data support.