EFFECT OF THYROID-HORMONES ON LP(A) AND LIPID-METABOLISM

The effect of thyroid hormones on lipoprotein(a) plasma concentrations and the other parameters of lipoprotein metabolism was studied in 158 patients with thyroid dysfunction and in 37 euthyroid controls (cross -sectional study). Multiple regression analysis revealed that 65.5 % o f the variability in lipoprotein(a) levels were predicted by changes i n lipoprotein(a) phenotypes (60.5 %), thyrotropin (3.5 %), and age (0. 8 %). The lipid parameters, however, showed no significant effect on l ipoprotein(a). A subgroup analysis on samples from patients with large lipoprotein(a) isoforms showed that 28 % of the variability in lipopr otein(a) concentrations could be explained by changes in thyroid funct ion (19.1 %), age (6.5 %) and triglycerides (3.5 %). Much stronger cor relations were found between thyrotropin and total cholesterol, low de nsity lipoprotein cholesterol or apolipoprotein B respectively (R-2 = 0.951 for low density lipoprotein cholesterol, R-2 = 0.801 for apolipo protein B). Our data suggest that thyroid hormone is a significant mod ulator of lipoprotein(a) metabolism. However, different mechanisms are responsible for the change in lipoprotein(a) levels and for the decre ase in total- and low density lipoprotein cholesterol levels.