Serum levels of free T3 are associated with ApoA1 and ApoA2, whereas free T4 levels are associated with ApoB and LDL-cholesterol in euthyroid cardiovascular patients

BackgroundThere are a few papers reporting the association between thyroid hormones, cholesterol and lipoprotein in euthyroid cardiovascular patients.ObjectiveOur objective was to investigate the relationship between thyroid hormones, cholesterol and lipoprotein in euthyroid cardiovascular patients.MethodsThe study population consisted of 73 consecutive euthyroid cardiovascular patients. The average age of the patients was 57 ± 16 years, and 52% were male. The serum levels of free 3,3′,5′-triiodo-l-thyronine (FT3), free thyroxine (3,5,3′,5′-tetraiodo-l-thyronine; FT4), thyroxine stimulating hormone (TSH), apolipoprotein, fatty acids and cholesterol were assessed.ResultsWe found a strong, significant positive correlation between the serum levels of FT4 and low-density lipoprotein cholesterol (LDL-C) (r = 0.442, p < 0.01), the serum levels of FT4 and apolipoprotein B (ApoB) (r = 0.402, p < 0.01), the serum levels of FT3 and apolipoprotein A2 (ApoA2) (r = 0.549, p < 0.01) and the serum level of TSH and high-density lipoprotein cholesterol (HDL-C) (r = 0.503, p < 0.01). There were significant positive correlations between the serum levels of TSH and ApoA1 (r = 0.267, p < 0.05), and the serum levels of TSH and apolipoprotein E (ApoE) (r = 0.302, p < 0.01). By contrast, there were significant negative correlations between the serum levels of TSH and triglyceride (TG) (r = − 0.315, p < 0.01) and the serum levels of TSH and docosahexaenoic acid (DHA) (r = − 0.274, p < 0.05).ConclusionsThis is the first report demonstrating a significant correlation between the serum levels of FT3 and both ApoA1 and ApoA2; the serum levels of FT4 and ApoA2, ApoB, TC and LDL-C; and the serum levels of TSH and ApoA1, ApoE, DHA, TG and HDL-C.