Objective: The aim of this study was to assess the serum levels of Lipoprotein(a) [Lp(a)] in subjects with thyroid disorders, as well as to investigate their relationship with lipid profile and the markers of thyroid function and autoimmunity, admitting that elevated Lp(a) levels and dyslipidemia caused by thyroid disorders synergistically increased the atherogenic process.
Methods: This study enrolled 38 subjects with hypothyroidism, 30 with hyperthyroidism and 55 with euthyroidism. The following parameters were measured: Lp(a), apolipoprotein AI (apo AI), apolipoprotein B (apo B), total cholesterol (TC), triglyceride (TG), low-density lipoprotein (LDL), high-density lipoprotein (HDL), very-low-density lipoprotein (VLDL), thyroid stimulating hormone (TSH), free thyroxine (FT4), triiodothyronine (T3), thyroid-peroxidase antibody (TPO-Ab).
Results: Lp(a) was found with increased mean serum levels in hypothyroid subjects (483.28 ± 281.55 mg/L). Hyperthyroid subjects showed normal levels (253.13 ± 94.29 mg/L) of Lp(a), but significantly lower than those with hypothyroidism and slightly increased levels in the euthyroid subjects (305 ± 100.44 mg/L). In hypothyroidism a significant positive correlation between Lp(a) and TSH, apo B, TC, TG, TC/HDL, VLDL levels and a negative correlation with FT4, T3 and apo AI/B (p < 0.05) was observed. No correlations were found between serum Lp(a) levels, lipids profile and thyroid function parameters in hyperthyroid subjects, neither with TPO-Ab.
Conclusions: The association of hypothyroidism with increased levels of Lp(a) seems to increase the already high cardiovascular risk in the hypothyroid subjects, while increased levels of Lp(a) represents independently a relevant cardiovascular risk factor.