Abstract
The impacts of thyroid hormones (TH) on lipid profile in euthyroid adults have gained much attention. It is currently unknown whether BMI influences such interaction. In the present study, we investigate the role of BMI in modulating the association between TH and lipid parameters in 1372 euthyroid healthy adults. Our results show that thyroid parameters are differentially associated with lipid profile. FT3 is positively correlated with total cholesterol (β = 0.176 ± 0.046, P < 0.001) and LDL cholesterol levels (β = 0.161 ± 0.040, P < 0.001). FT4 is negatively correlated with TG (β = −0.087 ± 0.029, P < 0.01) while positively correlated with HDL cholesterol levels (β = 0.013 ± 0.005, P < 0.01). TSH is positively associated with TG (β = 0.145 ± 0.056, P < 0.05) and total cholesterol levels (β = 0.094 ± 0.030, P < 0.01). Importantly, BMI modulates the effect of TH on lipid profile: the interaction of FT4 and BMI and the interaction of FT3 and BMI reach statistical significance in predicting TG and HDL cholesterol levels, respectively. Stratified according to BMI levels, most associations between TH and lipid profile are significant only in normal-weight group. In conclusion, in euthyroid adults, high normal FT3, TSH levels, and low normal FT4 levels are associated with unfavorable lipid profile. BMI mediates the effect of thyroid function on lipid profile in euthyroid adults.
Highlights
Dyslipidemia constitutes a major risk factor for premature atherosclerosis and cardiovascular disease (CVD), which is a major cause of morbidity and mortality in both developed and developing countries [1]
Several studies have shown that low normal FT4 or high normal TSH levels are associated with unfavorable lipid profile
Overt thyroid dysfunctions are associated with alternations in lipid metabolism [2,3,4,5]
Summary
Dyslipidemia constitutes a major risk factor for premature atherosclerosis and cardiovascular disease (CVD), which is a major cause of morbidity and mortality in both developed and developing countries [1]. Hyperthyroidism leads to a hypermetabolic state and increased lipolysis, which is characterized by weight loss, lower plasma levels of HDL cholesterol, LDL cholesterol, and leptin [2]. The impacts of thyroid hormones within normal ranges on lipid profile have been clarified [6,7,8,9,10]. FT3 within normal range is positively correlated to dyslipidemia: high normal FT3 is associated with a less favorable metabolic phenotype in pregnant women [10] and in general euthyroid population [6]. Several studies have shown that low normal FT4 or high normal TSH levels are associated with unfavorable lipid profile
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