High Cholesterol: Causes & Types

Reviewed by Andrew M. Freeman, MD, FACC, FACP
A high level of cholesterol in the blood is due to abnormal levels of lipoproteins, the particles that carry cholesterol in the bloodstream.

High cholesterol may be related to:

  • Diet
  • Weight
  • Lack of physical activity
  • Genetic factors
  • Presence of other diseases (diabetes, underactive thyroid, etc.)


Types of Cholesterol and Lipoproteins

Low-Density Lipoprotein (LDL) or Bad Cholesterol - Plaque Builder

When too much LDL circulates in the blood, it can slowly build up in the inner walls of the arteries that feed the heart and brain. Together with other substances, it can form plaque (or atheroma), a thick, hard deposit that can narrow the arteries and make them less flexible. This condition is known as atherosclerosis. As the artery narrows and hardens, less blood can get through causing ischemia, or a lack of necessary nutrients. If a clot or blockage forms in a narrowed artery, heart attack or stroke can result.


High-Density Lipoprotein (HDL) or Good Cholesterol - The Bad Cholesterol Eater

About one-fourth to one-third of blood cholesterol is carried by HDL. HDL cholesterol is known as "good" cholesterol, because high levels of HDL seem to protect against heart attack. Low levels of HDL (less than 40 mg/dL) also increase the risk of heart disease. HDL tends to carry cholesterol away from the arteries and back to the liver, where it's passed from the body—in a way it "eats" up the bad cholesterol. Some experts believe that HDL removes excess cholesterol from arterial plaque, slowing its buildup.


Triglycerides - Blood Fats

Triglyceride is a form of fat made in the body. Elevated triglycerides can be due to overweight/obesity, physical inactivity, cigarette smoking, excess alcohol consumption and a diet very high in carbohydrates (60 percent of total calories or more). Many times, people with diabetes have high triglycerides when their blood sugar is not well controlled. People with high triglycerides often have a high total cholesterol level, including a high LDL (bad) level and a low HDL (good) level. Many people with heart disease and/or diabetes also have high triglyceride levels.


Lp(a) Cholesterol

Lp(a) is a genetic variation of LDL (bad) cholesterol. A high level of Lp(a) is a significant risk factor for the premature development of fatty deposits in arteries. Lp(a) isn't fully understood, but it may interact with substances found in artery walls and contribute to the buildup of fatty deposits.

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