a class of lipoproteins frequently divided into hdl2 and hdl3 and the minor variant hdl1. Hdl promote transport of cholesterol from extrahepatic tissue to the liver for excretion in the bile. Synthesised by the liver as discoid nascent hdl particles lacking a lipid core, they accumulate a core of cholesterol esters during reverse cholesterol transport and transfer them to the liver directly or indirectly via other lipoproteins. Hdl also shuttle apolipoproteins c-II and e to and from triglyceride-rich lipoproteins during catabolism of the lipoproteins. Serum hdl cholesterol has been negatively correlated with premature coronary heart disease.