| Purpose 1.Through designing a cross-sectional study,the goal is to explore the relationship between thyroid function and the prevalence of carotid atherosclerosis in euthyroid population.This will provide basic data for further exploring the effect of thyroid function indexes on carotid atherosclerosis.2.Through designing a cohort study,the goal is to assess the relationship between the baseline and longitudinal trends in thyroid function and incident carotid atherosclerosis assessed in euthyroid population;receiver operating characteristic(ROC)curves and the area under the curve(AUC)were used to assess the diagnostic capability of thyroid function for incident carotid atherosclerosis and calculate its cutoff values to predict incident carotid atherosclerosis.3.In order to assess the relationship between the baseline and longitudinal trends in thyroid function and carotid atherosclerosis,a nested case-control study design based on propensity score matching was used.The new carotid atherosclerosis patients were matched with a control group having similar baseline characteristics.Further clarification of the impact of thyroid function indicators on the incidence of carotid atherosclerosis was investigated.Method 1.This study participants were recruited from the Tianjin Chronic Low-grade Systemic Inflammation and Health Cohort Study from 2013 to 2019 in Tianjin,China.Free triiodothyronine(FT3),thyroxine(FT4),and thyroid-stimulating hormone(TSH)were measured using chemiluminescence immunoassay.Carotid atherosclerosis was assessed using ultrasonography.Thyroid function and ultrasonography were assessed yearly during follow-up.2.Multiple logistic regression models were used to assess the relationship between thyroid function and carotid atherosclerosis.3.Cox proportional hazards regression models were used to evaluate the relationship between the baseline,mean and change of FT3,FT4 and TSH and the incidence of carotid atherosclerosis.The ROC curves and AUC were used to evaluate the predictive value of thyroid function index on the incidence of carotid atherosclerosis,and the cutoff values were calculated.4.Using propensity score matching methods,the new carotid atherosclerosis patients were matched with a control group with similar baseline characteristics.Conditional logistic regression analysis was used to assess the baseline and longitudinal trends in thyroid function and carotid atherosclerosis.Results 1.Cross-sectional analysis results 14,406 euthyroid subjects were included in the present study,5,013 subjects had carotid atherosclerosis,and the prevalence was 30.9%.After adjusting for multiple confounding factors,the adjusted odds ratio(OR)(95% confidence interval(CI))of carotid atherosclerosis for per unit increase in FT3,FT4 and TSH concentrations were 1.11(1.02,1.20)(P=0.01),1.05(1.03,1.07)(P<0.0001),and 1.04(0.99,1.08)(P=0.10),respectively.2.Cohort study analysis results 3,543 participants were enrolled in the cohort study.During the 6-year follow-up period(median: 4.2 years),955 people were newly diagnosed with carotid atherosclerosis,the incidence rate of carotid atherosclerosis was 111 per 1,000 personyears.After adjusting for multiple confounding factors,the adjusted hazards ratio(HR)(95% CI)of incident carotid atherosclerosis for per unit increase in FT3,FT4 and TSH concentrations were 1.12(0.99,1.28)(P=0.08)),1.01(0.98,1.04)(P=0.59),0.97(0.90,1.05)(P=0.45),respectively.The adjusted HR(95% CI)of incident carotid atherosclerosis for per unit increase in mean of FT3,FT4 and TSH concentrations were 1.35(1.22,1.49)(P<0.0001),1.16(1.12,1.20)(P<0.0001),0.93(0.86,1.02)(P=0.11),respectively.The adjusted HR(95% CI)of incident carotid atherosclerosis for per unit increase in annual change of FT3,FT4 and TSH concentrations were 1.34(1.22,1.47)(P<0.0001),1.22(1.19,1.25)(P<0.0001),0.92(0.77,1.09)(P=0.32).The AUC for mean of FT3,FT4 levels diagnose incident carotid atherosclerosis was 0.57(0.55,0.59)and 0.59(0.57,0.61)(all P<0.0001)The cutoff values for mean of FT3 and FT4 levels predict carotid atherosclerosis were 4.89 pmol/L and 14.86 pmol/L;the AUC for annual change of FT3,FT4 levels diagnose incident carotid atherosclerosis were 0.51(0.49,0.53)(P=0.52)and 0.56(0.54,0.58)(P<0.0001),the cutoff values for annual change of FT3 and FT4 levels were 6.22 pmol/L and 0.26 pmol/L,respectively.3.Analysis results of nested case-control studies based on propensity scores matching After propensity scores matching,948 new-onset carotid atherosclerosis and 948 control were generated.The present results showed that baseline FT3,FT4,and TSH levels were not related to carotid atherosclerosis(all P>0.05).The mean of FT3 and FT4 levels were significantly positively related to carotid atherosclerosis(all P<0.01),however,the mean of TSH was not related to carotid atherosclerosis(P>0.05).The annual change of FT3 and FT4 levels were significantly positively related to carotid atherosclerosis(all P<0.0001),however,the mean of TSH was not related to carotid atherosclerosis(P>0.05).Conclusions 1.The prevalence of carotid atherosclerosis(30.8%)is still high in euthyroid subjects.Even among euthyroid subjects,thyroid function is related to the prevalence of carotid atherosclerosis,of which FT3 and FT4 levels are positively related to the prevalence of carotid atherosclerosis,but the relationship between TSH levels and prevalence of carotid atherosclerosis was not found.In addition to the traditional influencing factors,this study explores new influencing factors related to carotid atherosclerosis and provides new ideas for the prevention and control of carotid atherosclerosis.2.The mean and annual change of FT3 and FT4 levels during the follow-up period were positively related to the incidence of carotid atherosclerosis,however no relationship was found between the baseline FT3 and FT4 levels and the incidence of carotid atherosclerosis.Moreover,this study found no relationship between TSH levels(including baseline,mean and annual change)and carotid atherosclerosis.These results imply that persistently high serum FT3 and FT4 levels and/or continuously elevated serum FT3 and FT4 levels could increase the risk of carotid atherosclerosis.3.Compared with the change of FT3 and FT4 levels,the mean FT3 and FT4 levels could predict incident carotid atherosclerosis better.When the mean and annual change levels of FT3 and FT4 exceed the cutoff values,the risk of carotid atherosclerosis will increase.4.Through a nested case-control study based on propensity score matching,the study found that the means and annual change of FT3 and FT4 were still positively related to carotid atherosclerosis.The results of this study are similar with those of the cohort study.5.These findings suggest that it may be necessary to focus on the euthyroid population of subjects who have persistently high and/or continuously elevated serum FT3 and FT4 levels for the prevention and control of carotid atherosclerosis.Thyroid function may serve as a new marker for cardiovascular diseases and may provide scientific basis for the development of new drugs in the future. |
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