The Correlation Analysis Between TSH And Thyroid Hormones With BMI,Serum Lipid And HbA1c

BackgroundThe thyroid gland is one of vital glands in human,and it's well known that thyroid hormones modulate lipid and glucose metabolism.This study is designed to analyze the relationships between thyroid-related hormones(TSH,FT3,FT4)and body mass index(BMI),blood lipids in euthyroid.In addition,we also investigate the relationships of TSH,FT3 and FT4 with glycosylated hemoglobin(HbA1c)in euthyroid and subclinical hypothyroidism.MethodsWe collect cross-sectional data of 97,997 people,Using R software performe basic statistical analysis and modeling,The generalized additive models(GAM)and linear regression models are used to explain and present the relationships between thyroid-related hormones and BMI,blood lipids.and we also explore the association between TSH,FT3,FT4 and HbA1 c in euthyroid and subclinical hypothyroidism by GAM.ResultsThe GAM results show that TSH and FT3 increase with BMI increasing,and the effect of age and gender on the relationships between TSH,FT3 and BMI is statistically significant,while FT4 decrease with the increase of BMI,and the effect of age and gender on its relationship is neglectable.In the explore of the relationships between thyroid-related hormones and blood lipids,our results show that FT3 is positively correlated with TC in men after adjusting for age and BMI(? = 0.105,P < 0.05).In the study of the relationship between TSH,FT3,FT4 and HbA1 c,HbA1c is significantly higher in the subclinical hypothyroidism than euthyroid in men,and TSH has a linear negative relation with HbA1 c and FT3 has a non-linear negative relation with HbA1 c in euthyroid men,On the contrary,FT4 has a non-linear positive relation with HbA1 c in euthyroid men,and a non-linear relation with HbA1 c in subclinical hypothyroidism men.ConclusionsThere is a nonlinear positive correlation between TSH,FT3 and BMI in euthyroid,and these relationships are significantly affected by age and gender.After adjusting age and BMI,The linear relationship between FT3 and TC are significant in euthyroid men.TSH and FT3 only have statistically significant relation with HbA1 c in euthyroid men after age and BMI adjustment,FT4 has a non-linear relation with HbA1 c in euthyroiad men and.subclinical hypothyroidism men.