Study On The Effect Of FT3,FT4 And TSH On Blood Lipid Metabolism

Objective: To analyze the independent correlation between free triiodothyronine(FT3),free thyroxine(FT4)and thyroid stimulating hormone(TSH)in the normal range and various components of blood lipids,and mainly explore the role of FT3 in cholesterol metabolism.It will provide a basis for further research on the mechanism of thyroid hormones affecting blood lipids,and also provide clues for early detection and effective treatment of dyslipidemia in c linical work,thereby preventing cardiovascular disease.Methods: A total of 603 Chinese,aged ≥18 years,from a univers ity community in Nanning,Guangxi,were enrolled for a epidemiological investigation by random and cluster sampling method.Collected the basic information of each research object by questionnaires,inc luding gender,age,smoking and drinking status,eating habits,intens ity and duration of exercise,previous med ical history and family history,and drug use status.Each subject was given a physical examination,which inc luded measurements of height,weight,waist circumference,hips circumference,etc.Collect forearm elbow vein blood,and measure FT3,free thyroxine(FT4),thyroid stimulating hormone(TSH),serum total cholesterol(TC),high density lipoprotein cholesterol(HDL-C),triglycerides(TG),and fasting blood glucose(FPG)and fasting insulin.Finally,461 eligible research objects were enrolled.Statistical analysis : T test and Spearman correlation were used for bivariate correlation analysis.Gender,age,smoking,body mass index(BMI),waist-hip ratio,and homeostasis model assessment of insulin resistance(HOMA-IR)and other confounding factors were controlled.Multiple linear regression analysis was performed with FT3,FT4,and TSH as independent variables,and TC,HDL-C and TG as dependent variables.The receiver operating characteristic curve(ROC curve)was drawn to evaluate the diagnostic value of FT3 for abnormal cholesterol levels.p<0.05 was considered as statistically significant.Results: 1.FT3 was negatively correlated with TC and HDL-C,and positively correlated with TG.After controlling for mixed factors,FT3 was still significantly negatively correlated with TC and HDL-C levels.On average,for every 1pmol/L decrease in FT3,TC increased by 0.322mmol/L;while for every1pmol/L increase in FT3,HDL-C decreased by 0.113mmol/L.However,after controlling for confounding factors,there was no significant correlation between FT3 and TG levels.2.FT4 was negatively correlated with TC,but not significantly correlated with HDL-C and TG.After controlling for mixed factors,FT4 had no significant correlation with lipid.3.TSH was positively correlated with TG,but not significantly correlated with TC and HDL-C.After controlling for mixed factors,there was no significant difference in the correlation between TSH and lipid.4.The area under ROC curve(AUC)of FT3 diagnosis of elevated TC is 0.5558;the optimal cut-off point is 4.57pmol/L,which corresponds to a sensitivity of49.42% and a specificity of 61.39%.5.The AUC of FT3 diagnosis of HDL-C reduction is 0.6279;the optimal cut-off point is 4.20pmol/L,the corresponding sensitivity is 74.07%,and the specificity is 41.07%.Conclusion: FT3 is an important factor affecting cholesterol(TC and HDL-C)metabolism in people with normal thyroid function.The Decrease of FT3 levels within the normal range can lead to the increase of TC levels,and the optimal critical point is 4.57pmol/L;while the increase of FT3 levels leads to the decrease of HDL-C levels,and the optimal critical point is 4.20pmol/L.In clinical work,we must pay attention to the detection of thyroid function(especially FT3)in patients with hypercholesterolemia and low HDL-Cemia,and actively look for the primary diseases that cause dyslipidemia.At the same time,for people with abnormal thyroid function or FT3 at normal high or low levels,it is also necessary to monitor cholesterol levels,so as to early detection and treatment of dyslipidemia,prevention and treatment of cardiovascular diseases.