THYROID-HORMONE (FT4) REDUCES LIPOPROTEIN(A) PLASMA-LEVELS

To study the influence of thyroid hormone on Lp(a) plasma concentratio n we measured Lp(a), total cholesterol, LDL-C, HDL-C, triglycerides an d fT4 levels and determined apo(a) phenotypes in 26 patients with hype rthyroidism in a follow-up study before and after thyreostatic treatme nt. The pretreatment values of total cholesterol (TC), LDL-C, and Lp(a ) were significantly reduced as compared with those of healthy control s. The reduced mean Lp(a) concentrations could not be explained by a d ifference of apo(a) 'size allele' frequencies between patients and con trols. During thyreostatic treatment mean concentrations of TC, LDL-C, and HDL-C increased significantly. The mean Lp(a) value was not chang ed after 4 weeks of treatment. The individual changes of Lp(a), howeve r, correlated significantly with those of LDL-C levels (R = 0.40, P = 0.04). Eighty-one per cent of the patients showed an increase of Lp(a) or no change of the Lp(a) level and 19% reacted with a decrease upon thyreostatic treatment. The observed lipid and lipoprotein changes wer e not different in patients with Graves disease or multifocal toxic go iter. The results indicate that Lp(a) plasma levels are decreased in t he hyperthyroid state irrespective of the pathogenic mechanism.