Abstract
BACKGROUND: Thyroid dysfunction of any magnitude is associated with dyslipidemia. But the relationship of thyroid hormones with lipid parameters among euthyroid population is still unclear.
MATERIALS AND METHODS: This is a cross-sectional study to assess relationship between measured [free T3 (fT3), free T4 (fT4), and TSH] and derived (free T3/free T4 ratio, and TSH index) parameters of thyroid profile with different components of lipid profile among euthyroid population.
RESULTS: We included 100 patients (60 men and 40 women) in this study. The mean free T3, free T4, and TSH levels of our study population were 2.4 ± 0.5 pg/mL, 1.2 ± 0.2 ng/dL, and 3.0 ± 1.6 µIU/mL, respectively. Overall, fT3 had a significant positive correlation with HDL cholesterol (r = 0.4, p = 0.01) and a negative correlation with total cholesterol levels (r = -0.3, p = 0.04). While fT4 (r = 0.3, p = 0.04) and fT3/fT4 ratio (r = 0.5, p = 0.001) showed positive correlation only with HDL levels. In subgroup analysis, positive association of fT3 (r = 0.6, p = 0.008), fT4 (r = 0.4, p = 0.04), and fT3/fT4 ratio (r = 0.8, p = 0.001) with HDL cholesterol was significant only in men. And only in the subgroup with TSH ≥ 3 µIU/mL (N = 48), we found a significant negative correlation of fT3 with total cholesterol (r = -0.5, p = 0.01) and LDL levels (r = -0.7, p = 0.001) and a positive correlation with HDL levels (r = 0.5, p = 0.02).
CONCLUSION: Among euthyroid subjects, fT3 seems to have a significant and consistent favorable association with lipid levels, especially with HDL cholesterol. This positive association of fT3 with HDL is more marked in men and in subjects with TSH ≥ 3 µIU/mL.