High-density lipoprotein (HDL) is known as "good" cholesterol and seems to have a protective effect on the heart and blood vessels. While it's not known exactly how HDL protects the cardiovascular system, low levels of HDL are a known risk factor for heart attack and heart disease. There are several causes of HDL that should be considered when evaluating a person's health.
Genetic Diseases
Tangier disease is caused by a mutation in the coding for gene ABCA1. This gene is responsible for coding a protein that pumps cholesterol from the cells of the body. Tangier disease causes a buildup of cholesterol in the cells and very low levels of HDL.
Fish-eye disease is caused by a deficiency of lecithin-cholesterol acyltransferase (LCAT), which forms an ester from cholesterol molecules. An ester is a chemical compound that is built with an oxoacid and a hydroxyl compound. LCAT deficiency in fish-eye disease is known to cause low levels of high-density lipoprotein.
Lifestyle Factors
Several lifestyle factors can contribute to low HDL levels. Smoking, high-carbohydrate diets and obesity can cause a decrease in HDL, and can also increase total cholesterol or levels of low-density lipoprotein (LDL), which is known as "bad" cholesterol. According to the American Academy of Family Physicians, a high body mass index (BMI) is clearly related to a decrease in the amount of HDL in the blood. Additionally, weight gain can decrease the levels of HDL in the blood by 3 to 5 percent.
Medications
Some medications can lead to lower levels of HDL cholesterol with long-term use. Beta blockers and diuretics, which are often used to treat high blood pressure, are linked to decreased levels of HDL in the blood. Drugs that contain the hormones testosterone and progesterone can also cause reduced levels of HDL. People who use anabolic steroids for increasing muscle mass and strength should have a lipid profile done to monitor their lipid levels, as anabolic steroids are associated with a drop in HDL levels.
Medical Conditions
Medical conditions that affect the cardiovascular system and kidneys can cause low levels of HDL in the blood. Metabolic syndrome, also known as Syndrome X, can cause high blood pressure, low levels of HDL cholesterol and elevated triglyceride levels. Diabetes, insulin resistance and high blood pressure are also associated with low HDL levels. People with these conditions should control lifestyle factors for low HDL by exercising regularly, following a sensible diet and avoiding nicotine and excessive alcohol consumption.
Inactivity
Sedentary and inactive lifestyles are associated with low levels of HDL in the blood. As a result, regular exercise is necessary for preventing further decline of HDL levels. The U.S. Department of Health and Human Services defines regular exercise as 30 to 60 minutes of activity on most days of the week. In addition to improving HDL levels, physical activity can also reduce levels of bad cholesterol and triglycerides, which further reduces the risk of coronary artery disease.
