It has also been responsible for 17 Nobel Prizes, countless pages of reports in scientific journals and the popular press, and mounting anxiety on the part of health-conscious people. The human body contains about 100 g of cholesterol. Most of this is incorporated in the membranes from which cells are constructed and is an indispensable component of them. The insulating layers of myelin wound around neurons are especially rich in cholesterol. In far smaller quantities, but no less important, cholesterol is used to synthesize several steroid hormones, including the sex hormones estrogen , progesterone , and testosterone as well as the corticosteroids .
Cholesterol is also the precursor from which the body synthesizes vitamin D .
One of the major uses of cholesterol is the synthesis of bile acids . These are synthesized in the liver from cholesterol and are secreted in the bile . They are essential for the absorption of fat from the contents of the intestine. A clue to the importance of cholesterol is that most of the bile acids are not lost in the feces but are reabsorbed from the lower intestine and recycled to the liver. There is some loss, however, and to compensate for this and to meet other needs, the liver synthesizes some 1500-2000 mg of new cholesterol each day.