What is Cholesterol is part of lipids. Lipids are a diverse group of compounds linked together to classification convenience rather than a true chemical homogeneity. Plasma lipids are: cholesterol Free esterified cholesterol triglycerides phospholipids non-esterified fatty acids (NEFA) Cholesterol is present in tissues and blood is only a small part of food-borne, but otherwise is synthesized by the body. And the liver is the key organ of the metabolism of cholesterol. Cholesterol and bile acids are secreted by the bile. Approximately 50% of cholesterol and 97% of bile acids are reabsorbed and returned to the liver. The secretion and reabsorption of cholesterol depend on its solubility with bile acids. Cholesterol and bile acids then recirculate continuously between the intestine and liver, with a net loss in the stool. Cholesterol has several biological functions. From that: adrenal steroid hormones sex hormones androgen and estrogen provitamin D3 In cells cholesterol becomes part of the support structures and especially of cell membranes in lipid-proteidic complex. It therefore vitally important in the economy of the organism. Bile acids also necessary for the intestinal digestion and absorption of fats, which are not breakdown products of cholesterol eliminated by the biliary tract. Despite having important functions, however, cholesterol should not exceed, as we shall see, certain quantities. In the blood it is located for the most part (60-75%) linked to long-chain unsaturated fatty acids (cholesterol esters), and the remaining free. Despite the insolubility in aqueous media the cholesterol is maintained in the circulation as it is conveyed, together with other lipid-type substances, serum proteins, and particularly by some globulins (alpha and beta lipoproteins). The anatomical damage caused by dyslipoproteinemia are represented, mainly, atherosclerosis. As regards cholesterol, a portion of that total is related to LDL and HDL lipoproteins. We distinguish, therefore: the total cholesterol which is an index of liver function LDL or "bad" cholesterol since LDL protein deposit excess cholesterol on the artery walls, leading to the formation of atherosclerotic plaques. HDL or "good" cholesterol because HDL cholesterol pick up the protein from the walls of the arteries, preventing the formation of atherosclerotic plaques.