Relationship Between Serum Free T4 (FT4) Level And Dyslipidemia In Healthy Euthyroid Subjects

Objective:Thyroid hormone(TH) is a class of important endocrine hormones,that can regulate body growth and metabolism,it including 3,5,3'-triiodothyronine(T3) and tetraiodothyronine(T4) in two types of physiological activity.In the blood,thyroid hormone have only 1%of the content to the free state exist,that is,FT3 and FT4,and through the thyroid hormone receptors exert their physiological effects.Thyroid hormones have a broad target cells,as long as the cell membrane has Na-K-ATP enzyme,thyroid hormones will influence their substance metabolism and energy metabolism.Accompanied by abnormal thyroid function,including the change of blood lipoprotein,weight,blood pressure and glucose,these changes are related to the role of thyroid hormones in various organs and tissues.At present,little is known about the relationship between serum free thyroxine and dyslipidemia in healthy euthyroid subjects.Therefore we used the data from epidemiology to explore the hypothesis that serum free thyroxine are associated with dyslipidemia and the metabolic variables in healthy euthyroid subjects,and provided evidence for people who have different levels of serum free thyroxine to prevent dyslipidemia and metabolic diseases.Methods:Atotal of 822 adult inhabitants were asked to fullfill the questionnaire,subjects who have incomplete information and known thyroid disease and thyroid hormone drugs or taking anti-thyroid drug therapy,the use of thyroid function effects of the drug and patients with diseases such as liver and kidney were excluded.Finally,677 subjects were enrolled.Accepted physical examination,drawn vein blood.The sera were measured for serum free thyroxine(FT4),fasting plasma glucose(FPG),fasting insulin (FINS),total-cholesterol(TC),triglycerid(TG),HDL-cholesterol(HDL-C).Homeostasis model assessment for insulin resistance(HOMA-IR) was cauculated as fasting insulin times fasting glucose divided by 22.5.Body mass index(BMI) was calculated as the ratio between weight and height squared.According to FT4 level is divided into four groups,analysis the relationship of different levels of FT4 and dyslipidemia. Results:1.According to gender,we divided the data into two groups,we found that the level of FT4 is higer in male than in female,the level of TSH is higer in female than in male.2.In males,the TC,FPG,SBP,DBPand TSH were significantly different in different levels of FT4(P＜0.05);TC and TSH were lower in the lower FT4 levers than the higher FT4 levers(P＜0.05),FPG,SBP and DBP were higher in the lower FT4 levers than the higher FT4 levers(P＜0.05).In females,the TSH,TC,HDL-C,SBP,DBP and BMI were significantly different in different levels of FT4(P＜0.05);TC,BMI and TSH were lower in the lower FT4 levers than the higher FT4 levers(P＜0.05),SBP,DBP and HDL-C were higher in the lower FT4 levers than the higher FT4 levers(P＜0.05).3.After adjustment for age,in males,Serum free thyroxine are negatively correlated with TC(β=-0.089,P=0.029);in females,Serum free thyroxine are negatively correlated with TC and HOMA-IR(β=-2.159,P=0.031;β=-0.450,P=0.008),but positively correlated with HDL-C(β=3.102,P=0.002).Both male and female,TSH and lipid metabolism was no significant correlation.4.The logistic regression analysis suggest that the different levels of FT4 and dyslipidemia was no significant correlation in male,but the lower FT4 was low HDL-C occurred in the independent risk factors(OR=0.902,95%CI=0.011-0.921) in female.Conclusion:1.Serum free thyroxine was significantly different in gender,and FT4 was higher in male than in female.2.The relationship of serum free thyroxine and dyslipidemia was different in male and female in healthy euthyroid subjects.In male,FT4 are negatively correlated with TC.In females,FT4 are negatively correlated with TC and HOMA-IR,but positively correlated with HDL-C.FT4 have a significant correlation with lipid metabolism.And in the female,with the lower FT4 levels,increased the risk of the occurrence of low HDL-C.When women with a low level of FT4 should be concerned about the occurrence of dyslipidemia,particularly the occurrence of low HDL-C.This is probably for the prevention of dyslipidemia and cardiovascular and cerebrovascular diseases have important significance. 3.TSH and lipid metabolism was no significant correlation.