Cholesterol is an animal sterol found in the body tissues (and blood plasma) of vertebrates. It can be found in large concentrations within the liver, spinal cord, and brain. Cholesterolis an important component of the membranes of cells, providing stability. It is the major precursor for the synthesis of vitamin D, of the various steroid hormones, including cortisol,cortisone, and aldosterone in the adrenal glands, and of the sex hormones progesterone, estrogen, and testosterone. Cholesterol also has an important role for the brain synapses as well as in the immune system. In conditions featuring elevated low density lipoproteins (LDL), cholesterol often forms plaque deposits in the walls of arteries, a condition known as atherosclerosis, which is a major contributor to coronary heart disease and other forms of cardiovascular disease.