cholesterol [ ko-les´ter-ol ] bile acids steroid gallstone atheroma lipoproteins . Two important fractions of the serum lipoproteins are high-density lipoproteins (HDL) and low-density lipoproteins (LDL).



High levels of total serum cholesterol have been shown to be associated with a high risk for coronary artery disease and myocardial infarction. Research has drawn a distinction between HDL-C, the cholesterol carried on high-density lipoproteins and LDL-C, the cholesterol carried on low-density lipoproteins. The balance between HDL-C and LDL-C is more significant than the total concentration of cholesterol in the blood. The risk of coronary heart disease increases as LDL-C increases and HDL-C decreases.



Because HDL-C promotes the removal of excess cholesterol from the cells and its excretion from the body, it is thought to be beneficial rather than harmful. In contrast, LDL-C picks up cholesterol from ingested fats and from cells that synthesize it in the body and delivers it to blood vessels and muscles where it is deposited in the cells. The concentration of cholesterol in cells within the linings of the arteries contributes to the build-up of atherosclerotic plaques. (See also atherosclerosis



A third type of lipoprotein is known as very-low-density lipoprotein (VLDL). There is a preponderance of triglyceride and very little cholesterol in VLDL. Triglyceride is the basic type of lipid used for the storage of energy. The role of serum triglyceride in the formation of atherosclerotic plaques is not known. Those persons who are at high risk for heart disease, already have a heart condition, or are obese should limit the amount of fats and cholesterol in the foods they eat. LDL-C levels can be reduced by limiting dietary intake of saturated fat and cholesterol. Organ meats and egg yolks are high in cholesterol. HDL-C levels can be raised by exercise, stopping cigarette smoking, and losing excess body fat. Structure and metabolism of cholesterol. From Dorland's, 2000. Blood Cholesterol . Laboratory testing of cholesterol in the blood is often used as a preliminary test for a disorder of blood lipids. Although the normal values for total blood cholesterol vary according to age, diet, and nationality, levels above 200 mg/dl indicate a need for further testing and efforts to reduce the cholesterol level. In general, as the total cholesterol level rises above 150 mg/dl, the risk for coronary artery disease gradually increases. Persons with cholesterol levels above 260 mg/dl may require medication to lower their LDL-C levels and reduce the risk of heart disease.



Increased levels of cholesterol in the blood are found in cardiovascular disease and atherosclerosis, obstructive jaundice, hypothyroidism, nephrosis, and uncontrolled diabetes mellitus. Cholesterol exists in both a free and esterified form; the ratio of free to esterified cholesterol is significant in the diagnosis of certain diseases. For example, there is a markedly abnormal ratio of these two forms of cholesterol in hepatic biliary disease, infectious diseases, and extreme cholesterolemia.



Decreased levels of cholesterol in the blood are noted when there is malabsorption of cholesterol from the intestinal tract as in pernicious anemia, hemolytic jaundice, hyperthyroidism, and terminal cancer. a steroid alcohol found in animal fats and oils, bile, blood, brain tissue, milk, egg yolk, myelin sheaths of nerve fibers, liver, kidneys, and adrenal glands. It is a precursor ofandhormones, and it occurs in the most common type of, inof the arteries, in various cysts, and in carcinomatous tissue. Most of the body's cholesterol is synthesized by the liver, but some is obtained in the diet from animal-derived foods. Plant-derived foods are cholesterol-free. Cholesterol is not transported free in the blood but is bound to certain proteins to form. Two important fractions of the serum lipoproteins are high-density lipoproteins (HDL) and low-density lipoproteins (LDL).High levels ofserum cholesterol have been shown to be associated with a high risk for coronary artery disease and myocardial infarction. Research has drawn a distinction between HDL-C, the cholesterol carried on high-density lipoproteins and LDL-C, the cholesterol carried on low-density lipoproteins. Thebetween HDL-C and LDL-C is more significant than theof cholesterol in the blood. The risk of coronary heart disease increases as LDL-C increases and HDL-C decreases.Because HDL-C promotes the removal of excess cholesterol from the cells and its excretion from the body, it is thought to be beneficial rather than harmful. In contrast, LDL-C picks up cholesterol from ingested fats and from cells that synthesize it in the body and delivers it to blood vessels and muscles where it is deposited in the cells. The concentration of cholesterol in cells within the linings of the arteries contributes to the build-up of atherosclerotic plaques. (See also.)A third type of lipoprotein is known as very-low-density lipoprotein (VLDL). There is a preponderance of triglyceride and very little cholesterol in VLDL. Triglyceride is the basic type of lipid used for the storage of energy. The role of serum triglyceride in the formation of atherosclerotic plaques is not known. Those persons who are at high risk for heart disease, already have a heart condition, or are obese should limit the amount of fats and cholesterol in the foods they eat. LDL-C levels can be reduced by limiting dietary intake of saturated fat and cholesterol. Organ meats and egg yolks are high in cholesterol. HDL-C levels can be raised by exercise, stopping cigarette smoking, and losing excess body fat. Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.

cho·les·ter·ol ( kō-les'ter-ol ),

See also: 5-cholesten-3β-ol (cholestane with a 5,6 double bond and a 3β-hydroxyl group); the most abundant steroid in animal tissues, especially in bile and gallstones, and present in food, especially food rich in animal fats; circulates in the plasma complexed to proteins of various densities and plays an important role in the pathogenesis of atheroma formation in arteries; a precursor of steroid hormones.See also: lipoprotein ), Farlex Partner Medical Dictionary © Farlex 2012

cholesterol (kə-lĕs′tə-rôl′, -rōl′) n. A white crystalline substance, C 27 H 45 OH, that is found in animal tissues and various foods and is important as a constituent of cell membranes and a precursor to steroid hormones. Cholesterol is normally synthesized by the liver and is transported through the bloodstream by different types of lipoproteins, two of which (HDL and LDL) are routinely measured in blood tests. The American Heritage® Medical Dictionary Copyright © 2007, 2004 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.

cholesterol A 27-carbon precursor of steroid hormones and bile acids which is an integral component of cell membranes and plasma lipoproteins; it is a precursor of bile acids and important in the synthesis of steroid hormones. It is the main component of the most common type of gallstones and is a major constituent of arterial atheromas; increased cholesterol is associated with ASHD, CAD, increased risk of death due to acute MIs and strokes.



Sources

Animal fat, bile, blood, brain, milk, egg yolk, myelin sheaths, liver, kidneys, adrenal gland.



Metabolism

Cholesterol is absorbed from ingested foods—diets high in saturated (animal) fats increase cholesterol levels—and synthesised in the liver. HDL-C is metabolised efficiently, and thus is “good” cholesterol; “bad cholesterol”, LDL-C, is inefficently metabolised; when the total cholesterol (TC) is increased (usually = 200 mg/dL), it is common practice to measure the levels of HDL-cholesterol and LDL-cholesterol.



Lab

TC is measured in routine chemistry panels; cholesterol is transported in the circulation by carrier proteins, which are classified according to their density (HDL, LDL, VLDL) based on density-gradient ultracentrifugation.



High risk for ASHD

• TC > 6.21 mmol/L—US: > 240 mg/dL;

• LDL-C > 160 mg/dl;

• HDL-C < 35 mg/dl.

Borderline risk

• TC = 5.17–6.18 mmol/L—US: 200–239 mg/dL;

Low risk

• TC < 5.17 mmol/L—US: 200 mg/dL;

• LDL-Cl < 130 mg/dL;

• HDL-C > 55 mg/dL.



Increased in

Hypercholesterolemia, nephrotic syndrome, hypothyroidism, biliary cirrhosis, high saturated fats in diet.



Decreased in

Malnutrition, hyperthyroidism, colorectal CA.



Management, hypercholesterolemia

Diet (decreased saturated fats), weight loss, regular exercise, medications. A 27-carbon precursor of steroid hormones and bile acids which is an integral component of cell membranes and plasma lipoproteins; it is a precursor of bile acids and important in the synthesis of steroid hormones. It is the main component of the most common type of gallstones and is a major constituent of arterial atheromas; increased cholesterol is associated with ASHD, CAD, increased risk of death due to acute MIs and strokes.SourcesAnimal fat, bile, blood, brain, milk, egg yolk, myelin sheaths, liver, kidneys, adrenal gland.MetabolismCholesterol is absorbed from ingested foods—diets high in saturated (animal) fats increase cholesterol levels—and synthesised in the liver. HDL-C is metabolised efficiently, and thus is “good” cholesterol; “bad cholesterol”, LDL-C, is inefficently metabolised; when the total cholesterol (TC) is increased (usually = 200 mg/dL), it is common practice to measure the levels of HDL-cholesterol and LDL-cholesterol.LabTC is measured in routine chemistry panels; cholesterol is transported in the circulation by carrier proteins, which are classified according to their density (HDL, LDL, VLDL) based on density-gradient ultracentrifugation.High risk for ASHD• TC > 6.21 mmol/L—US: > 240 mg/dL;• LDL-C > 160 mg/dl;• HDL-C < 35 mg/dl.Borderline risk• TC = 5.17–6.18 mmol/L—US: 200–239 mg/dL;Low risk• TC < 5.17 mmol/L—US: 200 mg/dL;• LDL-Cl < 130 mg/dL;• HDL-C > 55 mg/dL.Increased inHypercholesterolemia, nephrotic syndrome, hypothyroidism, biliary cirrhosis, high saturated fats in diet.Decreased inMalnutrition, hyperthyroidism, colorectal CA.Management, hypercholesterolemiaDiet (decreased saturated fats), weight loss, regular exercise, medications. Segen's Medical Dictionary. © 2012 Farlex, Inc. All rights reserved.

cholesterol Biochemistry A precursor of steroid hormones and bile acids; it is an integral component of cell membranes and plasma lipoproteins, and found in animal fats, bile, blood, brain, milk, egg yolk, myelin sheaths, liver, kidneys, and adrenal glands; it is absorbed from the diet and synthesized in the liver; diets high in saturated–animal fats ↑ cholesterol levels; it is the main component of the most common type of gallstones, and integral to arterial atheromas, in cysts and in malignancy; it is a precursor of bile acids and important in the synthesis of steroid hormones; diets low in saturated fats ↓ cholesterol levels, as does exercise; ↑ cholesterol is associated with ASHD, CAD, ↑ risk of death due to acute MIs and strokes; total cholesterol–TC is measured in routine chemistry panels; cholesterol is transported in the circulation by carrier proteins, which are classified according to their density–high-density lipoprotein—HDL, LDL, VLDL, based on density gradient ultracentrifugation; HDL-C is metabolized efficiently, and thus is 'good' cholesterol; 'bad cholesterol,' LDL-C, is inefficently metabolized High risk for ASHD TC > 6.21 mmol/L–US > 240 mg/dL; LDL-C > 160 mg/dl, HDL-C

< 35 mg/dl Borderline risk 5.17-6.18 mmol/L–US: 200-239 mg/dL Low risk < 5.17 mmol/L–US 200 mg/dL, LDL-Cl < 130 mg/dL, HDL-C > 55 mg/dL ↑ in Hypercholesterolemia, nephrotic syndrome, hypothyroidism, biliary cirrhosis ↓ in Malnutrition, hyperthyroidism, colorectal CA Management, ↑ cholesterol Diet–↓ saturated fats, weight loss, regular exercise, medications. See Fish, Biochemistry A precursor of steroid hormones and bile acids; it is an integral component of cell membranes and plasma lipoproteins, and found in animal fats, bile, blood, brain, milk, egg yolk, myelin sheaths, liver, kidneys, and adrenal glands; it is absorbed from the dietsynthesized in the liver; diets high in saturated–animal fats ↑ cholesterol levels; it is the main component of the most common type of gallstones, and integral to arterial atheromas, in cysts and in malignancy; it is a precursor of bile acids and important in the synthesis of steroid hormones; diets low in saturated fats ↓ cholesterol levels, as does exercise; ↑ cholesterol is associated with ASHD, CAD, ↑ risk of death due to acute MIs and strokes; total cholesterol–TC is measured in routine chemistry panels; cholesterol is transported in the circulation by carrier proteins, which are classified according to their density–high-density lipoprotein—HDL, LDL, VLDL, based on density gradient ultracentrifugation; HDL-C is metabolized efficiently, and thus is 'good' cholesterol; 'bad cholesterol,' LDL-C, is inefficently metabolized High risk for ASHD TC > 6.21 mmol/L–US > 240 mg/dL; LDL-C > 160 mg/dl, HDL-C< 35 mg/dl Borderline risk 5.17-6.18 mmol/L–US: 200-239 mg/dL Low risk < 5.17 mmol/L–US 200 mg/dL, LDL-Cl < 130 mg/dL, HDL-C > 55 mg/dL ↑ in Hypercholesterolemia, nephrotic syndrome, hypothyroidism, biliary cirrhosis ↓ in Malnutrition, hyperthyroidism, colorectal CA Management, ↑ cholesterol Diet–↓ saturated fats, weight loss, regular exercise, medications. See Bad cholesterol Good cholesterol , HDL, Hypercholesterolemia LDL , RLP, VLDL McGraw-Hill Concise Dictionary of Modern Medicine. © 2002 by The McGraw-Hill Companies, Inc.

cho·les·ter·ol ( kŏ-les'tĕr-ol ) The most abundant steroid in animal tissues; circulates in the plasma complexed to proteins of various densities; plays an important role in the pathogenesis of atheroma formation in arteries. Medical Dictionary for the Health Professions and Nursing © Farlex 2012

cholesterol An essential body ingredient found in all human cells, mainly as part of the structure of the cell membranes. It is needed to form the essential steroid hormones, An essential body ingredient found in all human cells, mainly as part of the structure of the cell membranes. It is needed to form the essential steroid hormones, CORTISOL , corticosterone and ALDOSTERONE , the male and female sex hormones and the bile acids. It is synthesized in the liver and a large quantity of cholesterol passes down the bile duct into the intestine every day. Most of it is reabsorbed. A diet high in saturated fats encourages high blood cholesterol levels. Soluble dietary fibre and various drugs can bind intestinal cholesterol and prevent its reabsorption. Cholesterol is carried to the tissues in tiny cholesterol carriers called low density lipoproteins ( LDL s). Oxidation of these allows cholesterol to be deposited in the walls of arteries causing dangerous narrowing ( ATHEROSCLEROSIS ). Collins Dictionary of Medicine © Robert M. Youngson 2004, 2005

cholesterol a steroid that occurs in the cell membranes of animal cells, but not in plants. Cholesterol is produced in the liver and when in excess is excreted in the bile but is partly reabsorbed by the ileum. It may precipitate gallstones in the gallbladder or bile duct. Alternatively, if there is excess cholesterol in the blood, it may be deposited on the walls of the blood vessels, obstructing them and often leading to an intravascular clot which if it occurs in the region of the heart gives rise to a ‘heart attack’ or coronary thrombosis. Cholesterol is the precursor of animal steroid hormones and bile acids. a steroid that occurs in the cell membranes of animal cells, but not in plants. Cholesterol is produced in the liver and when in excess is excreted in the bile but is partly reabsorbed by the ileum. It may precipitate gallstones in the gallbladder or bile duct. Alternatively, if there is excess cholesterol in the blood, it may be deposited on the walls of the blood vessels, obstructing them and often leading to an intravascular clot which if it occurs in the region of the heart gives rise to a ‘heart attack’ or coronary thrombosis. Cholesterol is the precursor of animal steroid hormones and bile acids. Collins Dictionary of Biology, 3rd ed. © W. G. Hale, V. A. Saunders, J. P. Margham 2005

Cholesterol A fat-like substance that is made by the human body and eaten in animal products. Cholesterol is used to form cell membranes and process hormones and vitamin D. High cholesterol levels contribute to the development of atherosclerosis. Cholesterol-Reducing Drugs, Hypolipoproteinemia, Lipoproteins Test, Rickets, Vitamin D Deficiency Mentioned in: Atherosclerosis Gale Encyclopedia of Medicine. Copyright 2008 The Gale Group, Inc. All rights reserved.

cho·les·ter·ol ( kŏ-les'tĕr-ol ) The most abundant steroid in animal tissues; circulates in the plasma complexed to proteins of various densities; plays an important role in the pathogenesis of atheroma formation in arteries. Medical Dictionary for the Dental Professions © Farlex 2012