The effect of the treatment of hypothyroidism and hyperthyroidism on plasma lipids and apolipoproteins AI, AII and E

OBJECTIVE Although lipid abnormalities are well described in hypothyroidism, effects on apolipoproteins are less well understood, The aim of this study was to examine the effects of thyroid dysfunction on plasma lipids and apolipoproteins. DESIGN A prospective study of lipids and apolipoproteins before and after treatment of hypothyroidism and hyperthyroidism. PATIENTS Eighteen patients with hypothyroidism and 5 patients with hyperthyroidism were included. MEASUREMENTS Plasma cholesterol, triglycerides, HDL cholesterol, apo Al, apo All, and ape E were measured before and after treatment of the thyroid abnormality. RESULTS Total and HDL cholesterol, ape Al and apo E decreased with treatment of hypothyroidism, while triglycerides and ape All levels were unchanged. The total/HDL cholesterol and LDL/HDL cholesterol ratios also decreased with treatment of hypothyroidism. In contrast, treatment of hyperthyroidism was associated with an increase in total and HDL cholesterol, and ape Al, Triglycerides, ape All and Apo E were unchanged by treatment of hyperthyroidism. The total/HDL cholesterol and the LDL/HDL cholesterol ratios increased with treatment of hyperthyroidism. CONCLUSIONS Hypothyroidism and hyperthyroidism have opposite effects on plasma lipids and apolipoproteins, In hypothyroidism, total and HDL cholesterol, total/HDL cholesterol ratio, ape Al and ape E are elevated. The increase in ape Al without a concomitant increase in apo All suggests selective elevation of HDL2. In contrast, hyperthyroidism is associated with decreased total and HDL cholesterol, total/HDL cholesterol ratio, and ape Al levels, These effects are reversible with treatment of the underlying thyroid disorder.