(See also Overview of Cholesterol and Lipid Disorders.)
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 or strokes, 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 causes of elevated HDL levels are
Secondary causes of high HDL cholesterol include all of the following:
Chronic alcoholism without cirrhosis
An overactive thyroid gland (hyperthyroidism)
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 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.