[HDL--the unknown with great significance].

The high density lipoproteins (HDL) play an important role in lipoprotein metabolism. In view of the results of various epidemiologic and experimental studies, their antiatherogenic potency appears to be confirmed. The antiatherogenic effect of the HDL can be chiefly explained by the following mechanisms: 1. inhibition of uptake of cholesterol-rich low density lipoproteins (LDL) by the smooth muscle cells in the arterial wall, 2. mobilization of cholesterol deposits from the cells of the arterial wall, and 3. an important role in the catabolism of triglyceride-rich lipoproteins. There are many unanswered questions concerning the role of HDL in lipoprotein metabolism. Furthermore, methodological problems with HDL determination at present reduce their clinical relevance. Determination of HDL-cholesterol should therefore be confined to borderline cases of hypercholesteremia (cholesterol 240-300 mg/100 ml) to provide a further argument for or against lipid-lowering treatment.