The U-shaped Curve Of Serum Thyrotropin Level And Uric Acid Level

Objective: To explore the relationship between serum thyrotropin(thyroid stimulating hormone)and uric acid levels in euthyroid-function people in the coastal areas of Qingdao.Methods:A household survey was conducted to obtain general information of subjects including gender,age,length of residence,history of diseases and drugs.Height,weight,systolic blood pressure(SBP)and diastolic blood pressure(DBP)were measured.Blood samples were collected and assayed for thyroid stimulating hormone(TSH),free triiodothyronine(FT3),free thyroxine(FT4),cholesterol(TC),triglyceride(TG),low-density lipoprotein cholesterol(LDL-c),high-density lipoprotein cholesterol(HDL-c),free fatty acids(FFA),fasting blood glucose(FPG),C-peptide(CP),insulin(INS),glycated hemoglobin(HbA1c),creatinine(Cr),uric acid(UA).Body mass index(BMI)and glomerular filtration rate(eGFR)were calculated.A total of 778 individuals were enrolled including 174 with hyperuricemia(HUA group)and 604 with normal serum UA level(non-HUA group).T-test was used to compare the clinical data of the two groups.Univariate correlation analysis(Pearson analysis)was used to explore the correlations between TSH,FT3,FT4 and serum uric acid,glomerular filtration rate respectively.The relationship of serum TSH level and uric acid level were investigated by curve fitting and threshold effect analysis.Results:(1)Compared with the non-HUA group,the BMI,SBP,DBP,FT3,C-peptide,and insulin levels in the HUA group were significantly higher(P <0.01).There was a statistical difference in serum lipid levels between two groups(P<0.01).There was no significant difference in serum TSH level and FT4 level between two groups(P>0.05).(2)TSH and eGFR were negatively correlated(P(27)0.001).After adjusting for confounding factors FT3 or FT3 and FT4,the correlation remained.After adjustment for the confounding factor FT4,the correlation was not seen(P>0.05).Whether adjusting for confounding factors FT3 and(or)FT4 or not,the correlation was not seen between TSH and UA(P>0.05).Whether TSH and/or FT4 were adjusted or not,FT3 was significant positively correlated with eGFR and UA(P<0.001).Whether or not the confounding factor TSH or FT3 was adjusted,TSH annd FT4 were not radiologically related(P>0.05).After adjustment for TSH and FT3,FT4 was positively correlated with e GFR(P<0.001).Whether or not adjusted for TSH(P>0.05),FT4 and UA were radiologically related.After adjusting confounding factors FT3 or TSH and FT3,FT4 was negatively correlated with UA(P(27)0.05).and negatively correlated with UA(P=0.041).(3)By the generalized additive linear model analysis,it was found that with the increasing of TSH,serum uric acid decreased first and then increased after adjusting BMI,SBP,DBP,TC,TG,HDL-c,LDL-c,FPG,CP and INS.The relationship between TSH and UA was a U-shaped curve.The inflexion point fell on 2.0 uIU/L of TSH value at which the UA level was as the lowest as 317.4 ?mol./L(95% confidence interval [CI]: 301.3 to 333.5?mol./L).The value of the turning-point and the trend of the curve did not change after adjusting the confounding factors FT3 and FT4.Conclusion: The relationship between serum thyroid stimulating hormone level and uric acid level is a U-shaped curve in euthyroid-function population.