(See also Overview of Cholesterol and Lipid Disorders Overview of Cholesterol and Lipid Disorders The body needs fats (lipids) for growth and energy. It also uses them to synthesize hormones and other substances needed for the body’s activities. The body may deposit excess fat in blood vessels... read more .)
A high level of HDL cholesterol (the "good" cholesterol) may decrease the risk of heart attacks and strokes. However, HDL cholesterol levels may be increased in some genetic disorders. In these disorders, the high HDL level may not protect against heart attacks Acute Coronary Syndromes (Heart Attack; Myocardial Infarction; Unstable Angina) Acute coronary syndromes result from a sudden blockage in a coronary artery. This blockage causes unstable angina or a heart attack (myocardial infarction), depending on the location and amount... read more or strokes Overview of Stroke A stroke occurs when an artery to the brain becomes blocked or ruptures, resulting in death of an area of brain tissue due to loss of its blood supply (cerebral infarction). Symptoms occur suddenly... read more , probably because the disease also causes other changes in lipid levels and other abnormalities in the way the body breaks down food.
Elevated HDL levels may be
Primary: Caused by a genetic mutation
Secondary: Caused by another disorder
Primary causes of elevated HDL levels are
Genetic mutations that result in overproduction or decreased removal of HDL
Secondary causes of high HDL cholesterol include all of the following:
Drugs (for example, corticosteroids, insulin, phenytoin)
High HDL cholesterol levels are diagnosed with blood tests that measure lipid levels in the blood. If a high HDL level is found in a person who is not taking lipid-lowering drugs, doctors look for the cause of the elevation.
A disorder that is causing very high HDL levels is treated.
Cholesteryl ester transfer protein (CETP) deficiency
Cholesteryl ester transfer protein (CETP) deficiency is a rare autosomal recessive disorder caused by a mutation of the CETP gene. Because CETP helps in the transfer of cholesterol from HDL to other lipoproteins, CETP deficiency affects low-density lipoprotein (LDL) cholesterol levels and slows removal of HDL cholesterol from the blood. Affected people have no symptoms but have high HDL cholesterol in their blood. No treatment is necessary.
Familial hyperalphalipoproteinemia is an autosomal dominant disorder caused by various genetic mutations. The disorder is usually diagnosed when elevated HDL cholesterol levels are found during a routine blood test. Affected people have no symptoms. No treatment is necessary.