A Study Of The Relationship Between Serum Thyrotropin And Components Of The Metabolic Syndrome

Objective Thyroid dysfunction is a risk factor for cardiovascualr disease. Metabolic syndrome(MS)is a cluster of obesity,elevated glucose(diabetes mellitus or impaired fasting glycaemia),dyslipidemia(hypertriglyceridemia and/or high HDL-C)and hypertansion.They are at risk for type 2 diabetes mellitus and cardiovascualr disease.The incidence of MS is increasing rapidly along with the prevalence of obesity and diabetes mellitus.At present ,little is known about the relationship between insulin resistnece and thyroid function and the componentes of MS.Therefore we uesd the data from epidemiology to explore the hypothesis that thyrotropin is associated with components of the metabolic syndrome,and provided evidence for mild thyroid dysfunction and normal thyroid function to prevent diabetes mellitus and cardiovascular disease.Method A total of 1534 adult inhabitants were asked to fullfill the questionnaire in Dadong district of Shenyang,Subjects who were thyroid dysfunction and taking thyroid medication or medicine influencing the thyroid function were excluded.Finally,1399 subjects aged(18-85)years were enrolled and needed to fill the questionnaire in details,accepted physical examination, drawn vein blood,and completed OGTT. The sera were measured for thyrotropin ( TSH ), fasting plasma glucose ( FPG ) , OGTTBG2h, fasting insulin(FINS),triglyceride(TG), HDL-cholesterol. Homeostasis model assessment for insulin resistance ( HOMA-IR )(mIU*mmol/liter2) was cauculated as fasting insulin(mIU/liter) times fasting glucose(mmol/liter).Body mass index (BMI) was cauculated as the ratio between weight and height squared(in kg/m2).The Metabolic Syndromewas defined according to CDS criteria.According to the criteria of thyroid disease,we put theses subjects into hypothyroidism,hyperthyroidism, normal thyroid function,and then according to our team's foudings that TSH between 1.0-1.9 mIU/L was safe,we put the group of normal thyroid function into low(0.30.05).2.Comparison the components of MS between different serum TSH: hypothyroidism had significantly increased TG and decreased HDL-C when compared to those in the group of normal thyroid function(P=0.011,P=0.005 respectively).Other compinents of MS have no differences between patients of hypothyroidism,hyperthyroidism and normal thyroid function (P>0.05).3. Comparison the serum TSH between groups of MS and non-MS: Serum TSH in the group of Metabolic Syndrome was higher than which in the group of non-Metabolic Syndrome(2.542 vs. 2.224, P=0.009).4.The relationship between serum TSH within the reference range and the prevalence of MS and its components:within the reference range of serum TSH,adjustment for gender,age and HOMA-IR,comparing TSH of 1.00-1.90 mIU/L(moderate tertile of the reference range)with TSH of 1.90-4.80 mIU/L (upper tertile of the reference range),the odds ratio for overweight/obesity was 1.545(95%CI为1.181-2.022).Adjustment for gender and age,the relationship between serum TSH within the reference range and dyslipidemia was significant(P=0.031);but adjustment for HOMA-IR and BMI,this relationship was not significant(P=0.173).Adjustment for gender,age,HOMA-IR and BMI,the relationship between serum TSH within the reference range and the prevence of hypertension,elevated glucose and MS were not related(P>0.05).5.The relationship between serum TSH within the reference range and the components of MS:in the linear regression model,serum TSH is positively related with BMI(β=0.921,P=0.022),but not related with SBP,DBP,TG, HDL-C,FBG,OGTT BG2h(P>0.05).In the multiple linear regression,adjustment for gender,age,HOMA-IR and BMI,the relationship between serum TSH and BMI bacame more significant(β=1.316,P=0.001),the relationship between serum TSH and TG bacame significant(β=0.066, P=0.016),but the relationship between serum TSH and DBP was not significant(P=0.081).Further adjustment for BMI,the relationship between serum TSH and TG was not significant(P=0.096).Adjustment for gender,age,HOMA-IR and BMI,there were no significant relationships between serum TSH and SBP,DBP,TG,HDL-C,FBG,OGTT BG2h (P>0.05).6.Serum TSH within the reference range and insulin resistence : Adjustment for gender,age and BMI,there were no significant relationship between serum TSH and HOMA-IR(P>0.05).Serum TSH was related with FINS significantly(β=0.057,P=0.024),Adjustment for gender,age,the relationship was still existing(β=0.059,P=0.021),further adjustment for HOMA-IR,the relationship was not existing(P>0.05).7.Serum TSH within the reference range and waist circumference : adjustment for gender,age and HOMA-IR,serum TSH was positively related with waist circumference.Conclusions 1.The prevalence of hypertension was higher in the group of hypothyroidism than which in the group of normal thyroid function;2 . Hypothyroidism had significantly increased TG and HDL-C when compared to those in the group of normal thyroid function;3.The prevalence of Metabolic syndrome is 18.9%,among which 53.2% is men,46.8% is women;4.Serum TSH in the group of Metabolic Syndrome was higher than which in the group of non-Metabolic Syndrome;5.Within the reference range of TSH, the prevalence of one component of MS(overweight/obesity) was increasing along with serum TSH; 6.Serum TSH within the reference range was positively related with BMI; 7.Serum TSH increasing slightly maybe a risk factor of Metabolic Syndrome.