Risk Factors (Genetics & Inherited Conditions)
Individuals who smoke, are obese, eat foods that are high in cholesterol (such as red meat and full-fat dairy products), do not exercise, have high blood pressure, or have diabetes are at risk for hypercholesterolemia. If an individual has high cholesterol levels and a parent or sibling who developed heart disease before the age of fifty-five, the individual will have an increased risk of also developing heart disease.
It is evident that hypercholesterolemia is more common among certain ethnic groups. Cholesterol levels in people from northern European countries are higher than in those from southern Europe. Asians have lower cholesterol levels than Caucasians. A severe form of hereditary hypercholesterolemia called familial hypercholesterolemia typically does not respond to lifestyle changes.
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Etiology and Genetics (Genetics & Inherited Conditions)
There is no doubt that genes play an important role in the occurrence of hypercholesterolemia. Familial hypercholesterolemia is the best understood genetically. It displays autosomal dominant inheritance, which means that either parent with hypercholesterolemia has a high probability of passing it on. This disorder results from defects of the LDL receptor, which ensures the proper movement of LDLs. Thus, dysfunction of this receptor causes increased levels of LDL in the blood. The LDL receptor gene, which is located on the short arm of human chromosome 19, is prone to a variety of mutations that affect LDL metabolism and movement.
Apolipoprotein B (Apo-B) is a protein essential for cholesterol transport. Apo-B can be affected by both diet and genetics. Individuals with one or more specific genotypes (the genetic constitution of an individual) have much greater changes in cholesterol levels in response to diet than do other genotypes.
The other genetic cause is mutations in the gene for the enzyme cholesterol 7-alpha hydroxylase (CYP7A1), which is essential for the normal elimination of cholesterol in the blood. It initiates the primary conversion of cholesterol into bile acids in the liver. Mutations can cause an accumulation of cholesterol in the liver, as the primary route of converting cholesterol to bile acids is blocked. The liver responds to excessive cholesterol by reducing the number of receptors...
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Symptoms (Genetics & Inherited Conditions)
Hypercholesterolemia itself may be asymptomatic but can still be damaging to the vascular system. Excess amounts of cholesterol in the blood can build up along the walls of the arteries, which results in hardening and narrowing of the arteries, called atherosclerosis. Severe atherosclerosis can lead to a blockage of blood flow. Atherosclerosis in the heart causes cardiovascular disease (such as heart attacks). The result of atherosclerosis in the brain can be a stroke. Atherosclerosis can also occur in the extremities of the body, such as the legs, causing pain and blood clots.
Several diseases can contribute to hypercholesterolemia, such as diabetes, thyroid disorders, and liver diseases. However, the most important cause of hypercholesterolemia is a combination of diet and genetic factors.
Hypercholesterolemia is on the increase worldwide. People with hypercholesterolemia often develop coronary heart disease at a younger age than those in a general population as a result of increased LDL cholesterol levels (about two times higher than normal). In cases of extreme hypercholesterolemia (exceeding three or four times normal), high cholesterol levels can be detected in utero or at birth in cord blood. Individuals with extreme hypercholesterolemia usually develop the first cardiovascular event in childhood or adolescence and die by the age of thirty.
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Screening and Diagnosis (Genetics & Inherited Conditions)
Treatment and Therapy (Genetics & Inherited Conditions)
Although genetics plays an important role, hypercholesterolemia is often the result of a combination of genetics and lifestyle. Consuming a healthy diet and exercising regularly can help maintain an optimal cholesterol level and reduce the risk of cardiovascular disease for people with either a good gene or a bad gene.
If lifestyle changes fail to lower cholesterol levels, the doctor may recommend medication. Statins, such as atorvastatin (Lipitor), fluvastatin (Lescol), lovastatin (Altoprev, Mevacor), pravastatin (Pravachol), rosuvastatin (Crestor) and simvastatin (Zocor), are a commonly prescribed treatment. These drugs deplete cholesterol in liver cells, causing the liver to remove cholesterol from the blood. Bile-acid-binding resins, including cholestyramine (Prevalite, Questran), colesevelam (Welchol), and colestipol (Colestid), bind to bile acids in the liver. This causes the liver to use its excess cholesterol to produce more bile acids, reducing the levels of cholesterol in the blood.
Another class of drugs, like the drug ezetimibe (Zetia), are cholesterol absorption inhibitors. These drugs decrease the amount of dietary cholesterol that is absorbed in the small intestine and released into the bloodstream. Zetia can be used with any of the statin drugs. Similarly, the combination drug ezetimibe-simvastatin (Vytorin) decreases both the dietary cholesterol absorbed in the small intestine and the cholesterol...
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Prevention and Outcomes (Genetics & Inherited Conditions)
Individuals can control their cholesterol levels by eating low-fat diets, maintaining healthy body weights, exercising regularly, and not smoking. They should also receive cholesterol and triglyceride screening to identify and treat abnormal levels. This screening is recommended for men between the ages of twenty and thirty-five and women between the ages of twenty and forty-five.
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Further Reading (Genetics & Inherited Conditions)
Abrams, Jonathan, ed. Cholesterol Lowering: A Practical Guide to Therapy. London: Arnold, 2003. Written for the general reader, this guide summarizes clinical data, explains the rationale behind therapies that aim to lower blood lipid levels, and discusses the role of diet and lifestyle in maintaining these reduced levels.
Cohen, Jay S. What You Must Know About Statin Drugs and Their Natural Alternatives: A Consumer’s Guide to Safely Using Lipitor, Zocor, Mevacor, Crestor, Pravachol, or Natural Alternatives. Garden City Park, N.Y.: Square One, 2005. Explains how statins work, their possible side effects, and effective alternative treatments to lower cholestorol.
Freeman, Mason W., and Christine Junge. The Harvard Medical School Guide to Lowering Your Cholesterol. New York: McGraw-Hill, 2005. A consumer guide providing an explanation of cholesterol and its role in heart disease. Discusses how cholesterol can be reduced through diet, exercise, drugs, and alternative treatments.
Goldstein, J. L., H. H. Hobbs, and M. S. Brown. “Familial Hypercholesterolemia.” In The Metabolic and Molecular Bases of Inherited Disease, edited by C. R. Scriver et al. 7th ed. New York: McGraw-Hill, 1995. Describes the epidemiology and genetic background of familial hypercholesterolemia.
Rantala, M., et al. “Apolipoprotien B Gene Polymorphisms and Serum Lipids: Meta-Analysis and the Role...
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Web Sites of Interest (Genetics & Inherited Conditions)
American Heart Association. http://www.americanheart.org. Searchable site provides information on familial and hypercholesterolemia.
Genetics Home Reference, Hypercholesterolemia. http://ghr.nlm.nih.gov/condition = hypercholesterolemia. Offers information about hypercholesterolemia, including an explanation of its genetic aspects and inheritance patterns.
Medline Plus. http://www.nlm.nih.gov/medlineplus/ency/article/000403.htm. Provides basic information about high blood cholesterol and triglycerides, with links to additional resources.
University of Maryland Medical Center, Hypercholesterolemia. http://www.umm.edu/altmed/articles/hypercholesterolemia-000084.htm. Discusses the signs, symptoms, causes, risk factors, treatment, and other aspects of hypercholesterolemia.
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Causes and Symptoms (Magill’s Medical Guide, Sixth Edition)
It has been difficult for the medical profession to establish a clear, causal connection between high cholesterol in the blood and heart disease. Only by studying a large number of patients over an extended time, as was done at Framingham, Massachusetts, was it possible to establish a now widely accepted statistical correlation between high cholesterol and cardiovascular problems. Cholesterol is a fatty material similar to animal fats, which are called lipids. In the bloodstream, cholesterol lipids combine with proteins to form either a low-density lipoprotein (LDL) or high-density lipoprotein (HDL). LDL transports cholesterol from the liver and intestines to other parts of the body where it is needed. HDL transports excess cholesterol back to the liver, where it is metabolized and excreted. HDL prevents excess fat from being deposited on the walls of arteries and therefore is commonly called the “good” cholesterol. Research has established that LDL in blood should be less than 200 milligrams per deciliter, whereas HDL should be greater than 50 milligrams per deciliter, with a ratio of LDL to HDL of preferably four or less. A person is not aware of having high cholesterol. If the condition is not treated, however, then the likelihood of plaque buildup on artery walls and a possible blockage, causing a stroke or heart attack, is increased.
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Treatment and Therapy (Magill’s Medical Guide, Sixth Edition)
The first step to reduce excess cholesterol in the bloodstream is a change in diet. As a general guideline, the consumption of vegetables, fruits, and grains should be increased, while red meat, egg yolks, and high-fat dairy products should be decreased. Vegetable oils made from corn, olives, or soybeans, which are low in saturated fats, are preferable to butter and animal fats. The next step is to increase physical exercise, which generally raises HDL, the good cholesterol. Several prescription medications, such as Zocor or Lipitor, have been shown to be effective in lowering LDL. A physician needs to monitor a patient’s liver function to verify that no harmful side effects are occurring.
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Perspective and Prospects (Magill’s Medical Guide, Sixth Edition)
The 1985 Nobel Prize in Medicine was awarded to Michael Brown and Joseph Goldstein for their study of cell-surface receptors that control the entry of LDL into cells. They showed that some people have a deficiency of these receptors. As a result, LDL does not enter cells at the normal rate but continues to circulate in the bloodstream, where it then can adhere to artery walls. In the future, it may be possible to produce drugs that stimulate the body to make more LDL receptors, which would remove excess LDL from the bloodstream.
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For Further Information: (Magill’s Medical Guide, Sixth Edition)
American Medical Association. American Medical Association Family Medical Guide. 4th rev. ed. Hoboken, N.J.: John Wiley & Sons, 2004.
Cooper, Kenneth H. Controlling Cholesterol the Natural Way. New York: Bantam Books, 1999.
Kowalski, Robert E. The New Eight-Week Cholesterol Cure. New York: Harper & Row, 2006.
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Hypercholesterolemia (Encyclopedia of Medicine)
Hypercholesterolemia refers to levels of cholesterol in the blood that are higher than normal.
Cholesterol circulates in the blood stream. It is an essential molecule for the human body. Cholesterol is a molecule from which hormones and steroids are made. It is also used to maintain nerve cells. Between 75 and 80% of the cholesterol that circulates in a person's blood-stream stream is made in that person's liver. The remainder is acquired from outside sources. Cholesterol is found in animal sources of food. It is not found in plants.
Normal blood cholesterol level is a number derived by laboratory analysis. A normal or desirable cholesterol level is defined as less than 200 mg of cholesterol per deciliter of blood (mg/dL). Blood cholesterol is considered to be borderline when it is in the range of 200 to 239 mg/dL. Elevated cholesterol level is 240 mg/dL or above. Elevated blood cholesterol is considered to be hypercholesterolemia.
Cholesterol has been divided into two major categories: low-density lipoprotein (LDL), the so-called "bad" cholesterol, and high-density lipoprotein (HDL), the so-called "good" cholesterol. Diet, exercise, smoking, alcohol, and certain illnesses can affect the levels of both types of cholesterol. Eating a high fat diet will...
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