Plasma lipoprotein (a) concentrations in hypothyroid, euthyroid and hyperthyroid subjects

Objective - Alterations of the lipid profile are a well known phenomenon in thyroid dysfunction. Thyroid hormones regulate lipid metabolism through various mechanisms, but a key role is played by the LDL receptor pathway, Thyroid hormone influence on lipoprotein (a) [Lp(a)] metabolism is known. Methods and results - Therefore we studied Lp(a) concentrations in a group of 16 hypothyroid patients and in a group of 22 hyperthyroid patients. Twenty-six euthyroid subjects were used as a control group. Plasma Lp(a) concentrations in hyperthyroid patients (23.2 +/- 28.1 mg/dl) were significantly lower than those of the hypothyroid patients (27.1 +/- 19.2, p < 0.05), There were negative correlations between plasma Lp(a) concentrations and total T-4 levels in patients with hyperthyroidism and hypothyroidism (r: -0.49, P < 0.05; r: -0.40, P < 0.05, respectively). Also, decreased HDL-C levels, increased LDL-C, total cholesterol and apo B levels in the hypothyroid patients according to euthyroid subjects were observed (P < 0.05), Decreased LDL-C levels, increased HDL-C and apo Al levels in the hyperthyroid patients according to euthyroid subjects were determined (P < 0.05). Conclusions - It was concluded that plasma Lp(a) concentrations increase in hypothyroid patients and the observed relationships between thyroid status and Lp(a) levels can be explained by impaired catabolism of apo B and Lp(a) in hypothyroidism.