Establishment Of Normal Thyroid Function Reference Interval For Healthy Adults Of Different Ages And Genders In Xi'an Urban Area

Objectives:To study thyroid hormone levels among healthy people in Xi'an,to establish the reference range of thyroid function in healthy adults of different sex and age in the region,and to analyze the difference of thyroid function in different sex and age stage,so as to provide reliable basis for the diagnosis and treatment of thyroid disease and to improve the accuracy of diagnosis of disease.Methods:Collected from December 2017 to December 2019 in physical examination department of Xi'an Central Hospital for routine physical examination of1961 people.Collected general information,fasting cubital venous blood samples were takenforTT3,TT4,FT3,FT4,TSH,TPOAb,TgAb,andperformedthyroid ultrasound.According to the criteria for normal adult selection recommended by the National Academy of Clinical Biochemical Research Institute?NACB?,1218 people were classified into three groups by sex and age group:aged 18-40?male 268,female 190?,aged41-60?male 274,female 191?,aged>60?male 134,female 161?.All data were input into EXCEL form and analyzed using SPSS25.0.Kolmogorov-Smirnov was used to test the normality of the data,obeying the normal distribution data,the range of reference values is±1.96 s.The data that do not obey the normal distribution are expressed using the median(P_2.5^P_97.5),with reference values ranging from 95%confidence intervals.One-Way ANOVA or Kruskal-Wallis H was used to compare the differences between groups in each age group.The difference between male and female was statistically significant by independent sample t-test or Mann-Whitney U test to P<0.05the difference.Results:1.For male,TT3 levels gradually decreased with age,but there was no significant difference between groups?P=0.463>0.05?;TT4 levels were higher in the 41-60 age group and decreased after 60 years,but there was no significant difference between groups?P=0.562>0.05?;FT3 levels decreased significantly with age,and the differences between groups were statistically significant?P=0.000<0.05?;FT4 decreased with age,with statistically significant differences between 18-40 age group and 41-60 age group?P=0.000<0.05?,18-40 age group and over 60 age group?P=0.000<0.05?;TSH levels did not change significantly with age,and there was no significant statistical difference between age groups?P=0.817>0.05?.2.For female,TT3 levels showed a decreasing trend with age,with statistically significant differences between 18-40 age group and 41-60 age group?P=0.013<0.05?and 18-40 age group and over 60 age group?P=0.000<0.05?;TT4 levels did not change significantly before the age of 60,but a downward trend after age 60,among which the difference between 18-40 years old and over 60 years old was statistically significant?P=0.049<0.05?;FT3 levels decreased significantly with age,and the differences between groups were statistically significant?P=0.000<0.05?;FT4 gradually decreased with age,among which there were statistically significant differences between 18-40 years and41-60 years?P=0.048<0.05?,18-40 years and over 60 years?P=0.004<0.05?;TSH levels did not change significantly between the ages of 18-40 and 40-60,and a downward trend after age 60,but there was no significant statistical difference between age groups?P=0.046<0.05?.3.TT3 levels of men were higher than those of women in all age groups,among which there were gender differences and statistically significant differences in age groups41-60 years and older than 60 years?P=0.001<0.05?;TT4 levels were higher among females than among males in all age groups,with gender differences and statistical significance in the 18-40 age group?P=0.013<0.05?;FT3 levels of men were higher than those of women in all age groups,and gender differences were statistically significant?P=0.000<0.05?;The FT4 levels of men were higher than those of women in all age groups,with statistically significant differences between male and female aged18-40years?P=0.000<0.05?and 41-60years?P=0.015<0.05?;The TSH levels of women were higher than those of men in all age groups,with statistically significant differences betweenmaleandfemaleaged18-40years?P=0.000<0.05?and41-60years?P=0.001<0.05?.4.The normal reference range of TT3 were:18-40 years?male 1.21-2.47 nmol/L,female 1.21-2.43 nmol/L?;41-60 years?male 1.20-2.46 nmol/L,female 1.18-2.28nmol/L?;older than 60 years?male 1.05-2.53 nmol/L,female 0.94-2.36 nmol/L?.The normal reference range of TT4 were:18-40?male 63.40-137.64 nmol/L,female72.40-137.16 nmol/L?;41-60?male 65.02-138.32 nmol/L,female 67.67-141.41nmol/L?;greater than 60?male 60.97-138.27 nmol/L,female 61.87-138.27 nmol/L?.The normal reference range of FT3 were:18-40 years?male 4.35-6.43 pmol/L,female3.76-6.22 pmol/L?;41-60 years?male 3.88-6.50 pmol/L,female 3.58-5.82pmol/L?;greater than 60 years?male 3.44-6.22 pmol/L,female 2.98-5.84 pmol/L?.The normal reference range of FT4 were:18-40 years?male 13.38-22.04pmol/L,female12.97-21.01pmol/L?;41-60years?male12.62-21.32pmol/L,female12.13-20.79pmol/L?;greater than 60 years?male 21.21-20.91pmol/L,female11.92-20.58pmol/L?.The normal reference range of TSH were:18-40?male0.74-4.70uIU/ml,female 0.95-4.83uIU/ml?;41-60?male 0.78-4.57uIU/ml,female0.63-4.81uIU/ml?;older than 60?male 0.80-4.38uIU/ml,female 0.73-4.54uIU/ml?.Conciusions:1.In this study,the reference range of thyroid hormone for healthy adults in Xi'an urban area was established.2.There were sex differences in thyroid hormone levels,and also changes in different age groups.