The effect of D-thyroxine on lipoprotein lipids and apolipoproteins in primary type IIa hyperlipoproteinemia.

The effect of 3 months' treatment with D-thyroxine on the lipoprotein lipids and apolipoproteins AI and B was investigated in 12 patients with type IIa hyperlipoproteinemia. VLDL, LDL and HDL were separated by preparative ultracentrifugation. Both apolipoproteins were measured in serum by electroimmunoassay procedures with monospecific antisera. There was a significant decrease of cholesterol, phospholipids and apolipoprotein B in serum and of all lipids in the LDL class. VLDL and HDL lipids and apolipoprotein AI showed no significant alterations. The atherogenic ratios LDL/HDL lipids and apolipoprotein B/apolipoprotein AI were lowered with the most pronounced effect on the ratio between the two apoliopoproteins. It is concluded that there is an effective reduction of LDL particles by D-thyroxine. Further investigations are necessary to evaluate whether lipoprotein lipids or apolipoproteins are a better discriminator of the influence on atherosclerotic risk in type IIa hyperlipoproteinemia.