cholesterol (kәlĕs´tәrōl´´), fatty lipid found in the body
tissues and blood plasma of vertebrates; it is only sparingly
soluble in water, but much more soluble in some organic
solvents. A steroid, cholesterol can be found in large
concentrations in the brain, spinal cord, and liver. The liver
is the most important site of cholesterol biosynthesis, although
other sites include the adrenal glands and reproductive organs.
By means of several enzymatic reactions, cholesterol is
synthesized from acetic acid; it then serves as the major
precursor for the synthesis of vitamin D3, of the various
steroid hormones, including cortisol, cortisone, and aldosterone
in the adrenal glands, and of the sex hormones progesterone,
estrogen, and testosterone. Cholesterol is excreted from the
liver in the form of a secretion known as bile; it sometimes
crystallizes in the gall bladder to form gallstones. The
insolubility of cholesterol in water is also a factor in the
development of atherosclerosis (see arteriosclerosis), the pat