Disorders of Cholesterol Metabolism

Cholesterol is a white waxy sterol lipid that occurs in all animal cells. It has an important structural role in cell membranes, is the precursor for steroid hormones in the adrenal gland, and is the precursor for bile acids in the liver. Because of its insolubility in water, it is solubilized and transported in the blood as a lipoprotein complex. Cholesterol input to the body comes from the diet and endogenous synthesis, primarily by the liver. Cholesterol output occurs via secretion in the bile, conversion to bile acids, and loss from sloughing off of cells from the skin and intestines; a very small amount is lost in the urine. Lactating females also lose some cholesterol during breast feeding. The daily balance of cholesterol metabolism in humans is shown in Fig. 4–1.