The Relationship Between Serum Lipid And TSH Within The Referrence Range In Euthyroid Population

Objective:Thyroid function and TSH is associated with the level of serum lipid. And serum choleaterol may be associated with TSH even if the TSH is narrowed within the reference range.As we know, thyroid hormones are negatively associated with TSH, in our retrospection research, we focus on the association of serum lipid and TSH within the reference range after adjustment of thyroid hormones.Materials and Methods:We retrospectively reviewed 4848 subjects who were self-referred for a rountine health check-up at Provincial Hospital affiliated to Shandong University from January 2004 to December 2009. We exclude the persons in non-euthyroid status and those using thyroid medication to gain the euthyroid population. Finally,3664 euthyroid general population were evaluated.,they were divided in six groups according to serum TSH levels. Relations between TSH levels and lipids were analyzed by partial correlation analyses, general linear analysis, multivariate logistic regression analysis and multiple linear regression analysis.2 models were constructed in order to compare and adjust the effect of thyroid hormones:Model 1 was adjusted for gender,age, smoking status, BMI and FPG; Model 2 added thyroid hormones besides the factors in model 1.Result:1. There were significant differences in the composition of gender,smoking status and means of age,FPG,HDL-C,FT3,FT4,TT3,TT4 across the six groups, while other parameters had no statistically significant difference.2. After all confounding factors considered,the the linear coefficient was 0.017 (P=0.021), and the partial regression coefficient was 0.003 between logTC and TSH. Then we divided the population into 6 subgroups according to age, the relationship between TSH and TC was notobvious if the persons were younger than 50 years old, but the relationship became distinct in the elder population.3. In partial correlation analysis(model 2), the partial correlation coefficients between TSH and the log transform of LDL-C,HDL-C and TG were 0.049 (P= 0.005), -0.004 (P=0.818),0.059 (P-0.000). In general linear analysis,the linear coefficient were 0.011(p=0.281),-0.006 (p=0.529) and 0.074 (p=0.001) respectively(table3),which was consist with the partial correlation analysis. In multiple linear regression analysis, TSH was positive with LDL-C and TG, whose regression coefficients were 0.005(P=0.008) and 0.013 (P=0.001).4. The prevelance of hypercholesteremia in the 6 groups were showed a rising trend, but the difference made no statistically sense(P=0.322).Conclusion:In this study, we explore the relationship between TSH and serum lipid through the data from 3664 euthyroid subjects. We found there were positive associations between TSH and TC,LDL-C,LDL-C,TG,hypercholesteremia. Moreover, the relationship still remained the same after thyroid hormones adjusted. Beyond those results, we also discovered that TC showed a negative relationship with thyroid hormones in the multiple linear regression analysis. Finally, our data showed that TSH within the reference range was related with components of lipids. Besides, the correlation was stronger when the age became elder. This study is, to our knowledge, the first that addresses the possible linkage between TSH within reference range and serum lipids after the adjustment of thyroid hormones.