Lipoprotein (a) in Thyroid Dysfunction Before and After Treatment

 

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Summary

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 unknown; therefore we studied Lp(a) concentrations in a group of 29 hypothyroid patients with post-surgical hypothyroidism and in a group of 14 hyperthyroid subjects with Graves' disease before and after the thyroid function was normalized by treatment. In hypothyroid patients total and LDL-cholesterol markedly decreased after T4 treatment (342±78 mg/dl before and 193±46 mg/dl after; 225±72 mg/dl before, 111±43 mg/dl after respectively, p<0.001). Also HDL-cholesterol and triglycerides decreased (from 75±22 mg/dl to 56±18 mg/dl and from 182±87mg/dl to 112±42mg/dl respectively, p<0.001). Lp(a) showed minor but not significant variations (median values 80 mg/l before 55 mg/l after treatment, p: N.S.). In hyperthyroid patients total and LDL-cholesterol increased after methimazole treatment (from 148±49 mg/dl before to 254±67mg/dl after and from 87±38mg/dl before to 178±51 mg/dl after, p<0.001). HDL-cholesterol increased (from 39±9 to 50±15, p<0.01) while triglycerides were unchanged. Lp(a) levels slightly rose (median values 57 mg/l before 84 mg/l after treatment, p<0.05). These data suggest that the influence of thyroid hormones on Lp(a) metabolism is of minor entity and probably does not operate through the LDL receptor pathway.