Definition
Cholesterol is a fatty substance found in animal tissue and is an important component to the human body. It is manufactured in the liver and carried throughout the body in the bloodstream. Problems can occur when too much cholesterol forms an accumulation of plaque on blood vessel walls, which impedes blood flow to the heart and other organs. The highest cholesterol content is found in meat, poultry, shellfish, and dairy products.
Description
Cholesterol is the Dr. Jekyll and Mr. Hyde of medicine, since it has both a good side and bad side. It is necessary to digest fats from food, make hormones, build cell walls, and participate in other processes for maintaining a healthy body. When people talk about cholesterol as a medical problem, they are usually referring to high cholesterol.
This can be somewhat misleading, since there are four components to cholesterol. These are:
- LDL, the so-called bad cholesterol
- HDL, the so-called good cholesterol
- Triglycerides, a blood fat lipid that increases the risk for heart disease
- Total cholesterol
The U.S. Food and Drug Administration (FDA) estimates that 90 million American adults, roughly one-half of the adult population, have elevated cholesterol levels. High LDL (low-density lipoprotein) is a major contributing factor of heart disease. The cholesterol forms plaque in the heart’s blood vessels, which restricts or blocks the supply of blood to the heart, and causes a condition called atherosclerosis. This can lead to a heart attack, resulting in damage to the heart and possibly death.
Recently, chemical researchers found a link between cholesterol and Alzheimer’s disease. Reducing the amount of cholesterol in the cells appears to block attachment of senile plaques to the brain’s neurons. (The plaques begin the process that eventually kills brain neurons.) More study remains to test the effects of cholesterol on Alzheimer’s.
The population as a whole is at some risk of developing high LDL cholesterol in their lifetimes. Specific risk factors include a family history of high cholesterol, obesity, heart attack or stroke, alcoholism, and lack of regular exercise. The chances of developing high cholesterol increase after the age of 45. One of the primary causes of high LDL cholesterol is too much fat or sugar in the diet, a problem especially true in the United States. Cholesterol also is produced naturally in the liver and overproduction may occur even in people who limit their intake of high cholesterol food. Low HDL and high triglyceride levels also are risk factors for atherosclerosis.
Causes & symptoms
There are no readily apparent symptoms that indicate high LDL or triglycerides, or low HDL. The only way to diagnose a problem is through a simple blood test. However, one general indication of high cholesterol is obesity. Another is a high-fat diet. Recently, new research involving twins demonstrated that both genetic factors and diet contribute to cholesterol levels.
Diagnosis
High cholesterol often is diagnosed and treated by general practitioners or family practice physicians. In some cases, the condition is treated by an endocrinologist or cardiologist. Total cholesterol, LDL, HDL, and triglyceride levels as well as the cholesterol to HDL ratio are measured by a blood test called a lipid panel. The cost of a lipid panel is generally $40-100 and is covered by most health insurance and HMO plans, including
Medicare, providing there is an appropriate reason for the test. Home cholesterol testing kits are available over the counter but test only for total cholesterol. The results should only be used as a guide and if the total cholesterol level is high or low, a lipid panel should be performed by a physician. In most adults the recommended levels, measured by milligrams per deciliter (mg/dl) of blood, are: total cholesterol, less than 200; LDL, less than 130; HDL, more than 35; triglycerides, 30-200; and cholesterol to HDL ratio, four to one. However, the recommended cholesterol levels may vary, depending on other risk factors such as hypertension, a family history of heart disease, diabetes, age, alcoholism, and smoking.
Doctors have always been puzzled by why some people develop heart disease while others with identical HDL and LDL levels do not. New studies indicate it may be due to the size of the cholesterol particles in the bloodstream. A test called a nuclear magnetic resonance (NMR) LipoProfile exposes a blood sample to a magnetic field to determine the size of the cholesterol particles. Particle size also can be determined by a centrifugation test, where blood samples are spun very quickly to allow particles to separate and move at different distances. The smaller the particles, the greater the chance of developing heart disease. It allows physicians to treat patients who have normal or close to normal results from a lipid panel but abnormal particle size.
Treatment
A wide variety of prescription medicines are available to treat cholesterol problems. These include statins such as Mevacor (lovastatin), Lescol (fluvastatin), Pravachol (pravastatin), Zocor (simvastatin), Baycol (cervastatin), and Lipitor (atorvastatin) to lower LDL. A group of drugs called fibric acid derivatives are used to lower triglycerides and raise HDL. These include Lopid (gemfibrozil), Atromid-S (clofibrate), and Tricor (fenofibrate).
A new class of drugs was identified late in 2001 that work differently from the statin drugs. These drugs rely on compounds that bind to a sterol that regulates protein (called SCAP) and speeds up removal of cholesterol from the plasma (the fluid part of the blood.) Doctors decide which drug to use based on the severity of the cholesterol problem, side effects, and cost.
Expected results
High cholesterol is one of the key risk factors for heart disease. Left untreated, too much bad cholesterol can clog the blood vessels, leading to chest pain (angina), blood clots, and heart attacks. Heart disease is the number one killer of men and women in the United States. By reducing LDL, people with heart disease may prevent further heart attacks and strokes, prolong and improve the quality of their lives, and slow or reverse cholesterol buildup in the arteries. In people without heart disease, lowering LDL can decrease the risk of a first heart attack or stroke.
