Serum lipids in hypothyroid children: effect of disease and levothyroxine replacement therapy

Abstract

Hypothyroidism is associated with dislipidaemia and an increased risk of atherosclerosis. The aim of this study was to examine the effect of disease and long-term levothyroxine replacement therapy on serum lipids in hypothyroid children. We measured concentrations of total cholesterol, HDL-cholesterol LDL-cholesterol, triglycerides and thyroid-stimulating hormone in serum samples of 58 children with hypothyroidism (before and after therapy) and in 100 healthy controls. LDL-C and TC values were most markedly affected by the hypothyroid state. The values in the patients were on the average of 100% (LDL-C) and 54% (TC) higher than in the healthy controls. This finding is accordance with the known fact that LDL clearance is slower in hypothyroidism. TG concentrations were slightly higher (p<0.05) and HDL-C lower (p<0.02), but only in some age groups of patients. The effect of long-term L-T4 replacement on LDL-C and TC was quantitatively most pronounced. The values obtained in patients after therapy were markedly lower than before therapy and did not differ significantly from the values found in the corresponding age groups of healthy children. Significantly lower concentrations of HDL-C and TG after L-T4 administration were found only in children aged from 10 to 15 years. When we compared the lipid-lowering effect of L-T4 replacement therapy in normometabolic versus hypometabolic patients, we obtained a significantly greater effect on TC and LDL-C values in the normometabolic than in hypometabolic group (p<0.01). TC and LDL-C concentrations obtained in the L-T4 treated patients correlated well with the corresponding TSH levels (r = 0.770 and 0.725, respectively).