Relationship Between Serum TSH Level And Metabolic Parameters In The General Population

Objective:To explore the relationship between serum thyroid stimulating hormone?TSH?level and metabolic factors in the general population,euthyroid individuals and the elderly population respectively.Methods:2,480 subjects were enrolled from the National Survey of Thyroid Diseases and Diabetes of China from June to November in 2017.The total population and the elderly population were divided into normal thyroid function?NTF?and subclinical hypothyroidism?SCH?groups respectively,with the TSH value of 4.2 as the boundary.The euthyroid individuals were divided in four groups according to the quartiles of TSH as group A?n=305,0.3-1.3mmol/L?,group B?n=829,1.3-2.2mmol/L?,group C?n=673,2.2-3.2mmol/L?and group D?n=349,3.2-4.2mmol/L?.The anthropometric parameters and biochemical indicators including thyroid function and related antibody of thyroid disease were determined.The parameters between all groups were compared using analysis of variance.Pearson correlation analysis and multiple linear regression analysis were used to find whether there are correlations between these variables and the independent risk factors for TSH.Results:1.327 subjects were diagnosed with thyroid diseases,73 subjects of them were 65 years old or older.According to the analysis results of all the subjects collected,there are 11subjects with hyperthyroidism accounting for 0.44%,17 subjects with subclinical hyperthyroidism accounting for 0.68%,the prevalence of SCH was 11.6%.With the increase of age,the proportion of hypothyroidism increased both in men and women,the difference was significant(Male:X²=19.609,P<0.001,P_trend=0.001;Female:X²=11.485,P=0.003,P_trend=0.003).In addition,elevated thyroglobulin antibody?TgAb?population accounted for9%,thyroid peroxidase antibody?TPOAb?increased population accounted for 10.55%.There are 336 subjects aged 65 or older.Among them,there are 261 cases with normal thyroid function accounting for 77%,and 66 cases with subclinical hypothyroidism accounting for20%.2.Gender,age,high density lipoprotein and TgAb were the risk factors for hypothyroidism in the general population,gender,systolic blood pressure,TPOAb and urine iodine the risk factors for hypothyroidism in the young population,and gender and high density lipoprotein were the main risk factors for hypothyroidism in the middle-aged population.In all categories,women were risk factors for hypothyroidism.For the elderly over 65 years old,all the independent variables included in this study show no difference.3.2156 euthyroid subjects with normal serum TSH level were accounted for 86.8%.Systolic blood pressure in group D was significant higher than other three groups;group C displayed significant lower TPOAb levels than other three groups;group C had lower TgAb levels than group A and group D,but TgAb levels in group B was only lower than group A.Pearson linear regression analysis showed that SBP?r=0.068;P=0.002?is positively correlated to TSH,but total cholesterol?r=-0.043,P=0.047?and urine iodine?r=-0.043,P=0.045?were negatively correlated to TSH.Multiple stepwise regression analysis revealed that systolic blood pressure,urine iodine,waist circumference,body max index,total cholesterol,triglyceride and low density lipoprotein were independent predictors of serum TSH levels.Conclusion:The large population-based study demonstrates significant interaction between metabolic factors and TSH levels.Hypertension,lipid metabolism disorder and excessive iodine intake may increase thyroid disease in the euthyroid subjects.Weight status,lipid metabolism disorder may increase thyroid disease in the general subjects,especially the elderly subjects.