Lipid Profile

Cholesterol, triglycerides, and lipoproteins are measured to evaluate a person’s risk of developing atherosclerotic disease, especially if there is a family history of premature heart disease, or to diagnose a specific lipoprotein abnormality. Cholesterol and triglycerides are transported in the blood

by combining with plasma proteins to form lipoproteins.

The lipoproteins are referred to as low-density lipoproteins (LDLs) and high-density lipoproteins (HDLs). The risk of CAD increases as the ratio of LDL to HDL or the ratio of

total cholesterol (LDL _ HDL) to HDL increases. Although cholesterol levels remain relatively constant over 24 hours, the blood specimen for the lipid profile should be obtained after a 12-hour fast.

Cholesterol Levels. Cholesterol (normal level is less than 200 mg/dL) is a lipid required for hormone synthesis and cell membrane formation. It is found in large quantities in brain and nerve tissue. Two major sources of cholesterol are diet (animal products) and the liver, where cholesterol is synthesized.

Elevated cholesterol levels are known to increase the risk of CAD. Factors that contribute to variations

in cholesterol levels include age, gender, diet, exercise patterns, genetics, menopause, tobacco use, and stress levels.

LDLs (normal level is less than 160 mg/dL) are the primary transporters of cholesterol and triglycerides into the cell. One harmful effect of LDL is the deposition of these substances in the walls of arterial vessels. Elevated LDL levels are associated with a greater incidence of CAD. In people with known CAD or diabetes, the primary goal for lipid management is reduction of LDL levels to less than 70 mg/dL.

HDLs (normal range in men is 35 to 70 mg/dL; in women, 35 to 85 mg/dL) have a protective action. They

transport cholesterol away from the tissue and cells of the arterial wall to the liver for excretion. Therefore, there is an inverse relationship between HDL levels and risk of CAD.

Factors that lower HDL levels include smoking, diabetes, obesity, and physical inactivity. In patients with CAD, a secondary goal of lipid management is the increase of HDL levels to more than 40 mg/dL.

Triglycerides. Triglycerides (normal range is 100 to 200 mg/dL), composed of free fatty acids and glycerol, are stored in the adipose tissue and are a source of energy. Triglyceride levels increase after meals and are affected by stress. Diabetes, alcohol use, and obesity can elevate triglyceride levels.

These levels have a direct correlation with LDL and an inverse one with HDL