Cholesterol Levels are used to determine the risk for Coronary Heart Disease (CHD). Cholestrerol Levels are also used for evaluation of hyperlipidemias. Cholesterol is the main lipid associated with arteriosclerotic vascular disease. Cholesterol, however, is required for the production of steroids, sex hormones, bile acids, and cellular membranes. Most of the cholesterol we eat comes from foods of animal origin. The liver metabolizes the cholesterol to its free form, and cholesterol is transported in the bloodstream by lipoproteins. Nearly 75% of the cholesterol is bound to low-density lipoproteins (LDL), and 25% is bound to high-density lipoproteins (HDLs). Cholesterol is the main component of LDL and only a minimal component of HDL and very-low-density lipoprotein (VLDL). It is the LDL that is most directly associated with increased risk for CHD.
The purpose of cholesterol testing is to identify patients at risk for arteriosclerotic heart disease. Cholesterol testing is usually done as a part of a lipid profile, which also include tests for the measurement of Lipoproteins and Triglycerides Levels, because, by itself, cholesterol is not a totally accurate predictor of heart disease. There is considerable overlap in what are considered “normal” and “high-risk” levels. “Normal” levels have been derived from a group of patients who have no obvious evidence of CHD. However, this may not be accurate because these patients may have preclinical CHD and may not truly reflect a “no-risk” population.
There is considerable variation in cholesterol levels. Day-to-day cholesterol values in the same individual can vary by 15%. An 8% difference can even be identified within the same day. Positional changes can affect these levels. Levels can decrease by as much as 15% in the recumbent position. As a result, hospitalized patients can be expected to have lower levels than outpatients. Because of these significant variabilities, elevated results should be corroborated by repeating the study. The two results should be averaged to obtain an accurate cholesterol level for risk assessment.
Because the liver is required to metabolize ingested cholesterol products, subnormal cholesterol levels are indicative of severe liver diseases. Furthermore, because our main source of cholesterol is our diet, malnutrition is also associated with low cholesterol levels. Certain illnesses can affect cholesterol levels. For example, patients with an acute myocardial infarction (AMI) may have as much as a 50% reduction in cholesterol level for as long as 6 to 8 weeks.
Total cholesterol is used most accurately as a predictor of the risk for CHD when studied as part of the updated Framingham Coronary Prediction algorithm. This prediction model is used to determine a person’s risk for developing an ischemic event (angina, myocardial infarction, or myocardial death) over the course of the following decade. Besides cholesterol, other factors used to estimate risk for CHD include age, lipoproteins, blood pressure, cigarette smoking history, diabetes mellitus, and gender.
This risk model uses a system whereby points are given for each factor in the model. The total number of points is used to provide the patient’s CHD risk. By dividing the CHD risk by age-related data (comparative risk), a risk relative to peers can be calculated. The CHD risk can be used to determine whether or not medicinal cholesterol lowering intervention is indicated.
Normal Cholesterol Levels
Newborns have the lowest Normal Cholesterol Levels. Normal Cholesterol Levels gradually increase as people advance in age. The following are the Normal Cholesterol Levels ranges for each age group:
Newborns: Normal levels range between 53 and 135 mg/dL.
Infants: Normal Cholesterol ranges between 70-175 mg/dL.
Children: Between 120 and 200 mg/dL.
Adults: More than 200 mg/dL.
Preparation for Measuring Cholesterol Levels
- Fat intake plays a role in increasing Cholesterol Levels. Patients should understand that dietary intake for 2 weeks before testing will affect results. It is suggested that the patient eat a normal diet for at least 1 week before testing.
- Alcohol consumption also affect the measurement of Cholesterol Levels. Patients who digest alcohol should stop it for at least 24 hours before the test. Patients are also required to fast between 12 to 14 hours before measuring Cholesterol Levels, only water is allowed during the fasting period.
False Indications of Cholestrol Levels
- Pregnancy is usually associated with High Cholesterol Levels.
- Oophorectomy and Postmenopausal status are associated with High Cholesterol Levels.
- Recumbent Position is associated with Low Cholesterol Levels.
- Drugs that may cause High Cholesterol Levels include Adrenocorticotropic Hormone, Anabolic Steroids, Beta-adrenergic Blocking agents, Corticosteroids, Cyclosporine, Epinephrine, Oral Contraceptives, Phenytoin (Dilantin), Sulfonamides, Thiazide Diuretics, and Vitamin D.
- Drugs that may cause Low Cholesterol Levels include Allopurinol, Androgens, Bile salt-binding Agents, Captopril, Chlorpropamide, Clofibrate, Colchicine, Colestipol, Erythromycin, Isoniazid, Liothyronine (Cytomel), Monoamine Oxidase Inhibitors, Niacin, Nitrates, and Statins.
Causes of High Cholesterol Levels
- Enzymatic deficiencies in lipid metabolism are associated with High Cholesterol Levels. High Cholesterol Levels can result from either Familial Hypercholesterolemia or Familial hyperlipidemia.
- High-cholesterol Diet: High intake of cholesterol leads to High Cholesterol Levels in the blood.
High Cholesterol Levels are also associated with the following conditions. However, the pathophysiology of the association of Cholesterol with these diseases is not well understood. The association has been only made by observation:
- Uncontrolled Diabetes Mellitus.
- Nephrotic Syndrome.
- Myocardial Infarction (MI).
- Biliary Cirrhosis and Extrahepatic Biliary.
- Nephrotic Syndrome.
Causes of Low Cholesterol Levels
Most of the cholesterol is synthesized from fat eaten in the diet. When dietary intake is decreased, fat levels and subsequently Cholesterol Levels fall as been observed with the following conditions:
- Advanced Cancer.
Low Cholesterol Levels are also associated with the following situations. However, The pathophysiology of the association of cholesterol levels with these situations is not well known. The association has been made by statistical observation:
- Cholesterol-lowering Medication.
- Pernicious Anemia.
- Hemolytic Anemia
- Liver Disease.
- Acute Myocardial Infarction (AMI).