‘Good’ Cholesterol Runs in the Family

Oct 29, 2004 11:58 AM EDT

A recent study has discovered two genetic defects that may contribute to low levels of ‘good’ cholesterol in the blood.

The study, published in a recent issue of Circulation Research, followed a family that has premature heart disease but normal cholesterol levels.

Risk may still increase with low HDL

University of Maryland School of Medicine researchers studied the family whose members had low HDL, or ‘good’ cholesterol levels. Scientists once believed that heart attacks did not occur when total cholesterol levels were under 150 mg/dl. However, recent studies suggest that, despite healthy levels of cholesterol, heart disease risk may still increase if levels of HDL are too low—as they were with the family in the study.

Scientists have been studying two genes that are responsible for low HDL levels for several years. Within the last five years, research has discovered mutations in a gene called ABCA1. This gene plays a role in the regulation of cholesterol and HDL metabolism. Further study has found two defects in this gene that would decrease the HDL levels to an extremely low range. Researchers say the family they are studying has these defects, which causes them to have low HDL levels.

Low HDL is most common abnormality

While medications are available to reduce the progression of heart disease, researchers have yet to determine how to reverse the condition which may come down to HDL levels. Further research is needed at this time.

High-density lipoprotein (HDL) is considered the ‘good’ form of cholesterol. The average HDL for men is about 45 mg/dl and about 55 mg/dl for women. Anything less than 35 is considered low and if the level is below 20, it's considered extremely low. Low HDL is the most common cholesterol abnormality in heart disease patients—but an extremely low HDL level only occurs in 1% of the population.


1. Seung Ho Hong; et al, “Novel Polypyrimidine Variation in ABCA1 Causes Exon Skipping and Contributes to HDL Cholesterol Deficiency in a Family with Premature Coronary Disease,” Circulation Research, 93: 1006 - 1012.