Cholesterol (cont.)
Why is HDL the good cholesterol?
HDL is the good cholesterol because it protects the arteries from the
atherosclerosis process. HDL cholesterol extracts cholesterol particles from the
artery walls and transports them to the liver to be disposed through the bile.
It also interferes with the accumulation of LDL cholesterol particles in the
artery walls.
The risk of atherosclerosis and heart attacks in both men and is strongly
related to HDL cholesterol levels. Low levels of HDL cholesterol are linked to a
higher risk, whereas high HDL cholesterol levels are associated with a lower
risk.
Very low and very high HDL cholesterol levels can run in families. Families
with low HDL cholesterol levels have a higher incidence of heart attacks than
the general population, while families with high HDL cholesterol levels tend to
live longer with a lower frequency of heart attacks.
Like LDL cholesterol, life style factors and other conditions influence HDL
cholesterol levels. HDL cholesterol levels are lower in persons who smoke
cigarettes, eat a lot of sweets, are overweight and inactive, and in patients
with type II diabetes mellitus.
HDL cholesterol is higher in people who are lean, exercise regularly, and do
not smoke cigarettes. Estrogen increases a person's HDL cholesterol, which
explains why women generally have higher HDL levels than men do.
For individuals with low HDL cholesterol levels, a high total or LDL
cholesterol blood level further increases the incidence of atherosclerosis and
heart attacks. Therefore, the combination of high levels of total and LDL
cholesterol with low levels of HDL cholesterol is undesirable whereas the
combination of low levels of total and LDL cholesterol and high levels of HDL
cholesterol is favorable.
What are LDL/HDL and total/HDL ratios?
The total cholesterol to HDL cholesterol ratio (total chol/HDL) is a number
that is helpful in estimating the risk of developing atherosclerosis. The number
is obtained by dividing total cholesterol by HDL cholesterol. (High ratios
indicate a higher risk of heart attacks, whereas low ratios indicate a lower
risk).
High total cholesterol and low HDL cholesterol increases the ratio and is
undesirable. Conversely, high HDL cholesterol and low total cholesterol lowers
the ratio and is desirable. An average ratio would be about 4.5. Ideally, one
should strive for ratios of 2 or 3 (less than 4).
What are the treatment guidelines for low HDL cholesterol?
In clinical trials involving lowering LDL cholesterol, scientists also
studied the effect of HDL cholesterol on atherosclerosis and heart attack rates.
They found that even small increases in HDL cholesterol could reduce the
frequency of heart attacks. For each 1 mg/dl increase in HDL cholesterol, there
is a 2 to 4% reduction in the risk of coronary heart disease. Although there are
no formal NCEP (please see discussion above) target treatment levels of HDL
cholesterol, an HDL level of <40 mg/dl is considered undesirable and measures
should be taken to increase it.
How can levels of HDL cholesterol be raised?
The first step in increasing HDL cholesterol levels (and decreasing LDL/HDL
ratios) is therapeutic life style changes. When these modifications are
insufficient, medications are used. In prescribing medications or medication
combinations, doctors have to take into account medication side effects as well
as the presence or absence of other abnormalities in cholesterol profiles.
Regular aerobic exercise, loss of excess weight (fat), and cessation of
smoking cigarettes will increase HDL cholesterol levels. Regular alcohol
consumption (such as one drink a day) will also raise HDL cholesterol. Because
of other adverse health consequences of excessive alcohol consumption, alcohol
is not recommended as a standard treatment for low HDL cholesterol.
Medications that are effective in increasing HDL cholesterol include
nicotinic acid (niacin), gemfibrozil (Lopid), estrogen, and to a much lesser
extent, the statin drugs (discussed below). A newer medicine, fenofibrate
(Tricor) has shown much promise in selectively increasing HDL levels and
reducing serum triglycerides.
Next: What are triglycerides, chylomicrons, and VLDL? »
- Statins - Read about statins, cholesterol lowering medications like Levacor, Zocor, Pravachol, Lipitor, Crestor, and more. Side effects, drug interactions, and patient information is also provided.
- Homocysteine - Read about the test for homocysteine levels in the blood. High levesl of homocysteine include increased risk of heart attacks, strokes, blood clots, and Alzheimer's disease.
- Diabetes - Learn about type 1 and 2 diabetes (Diabetes Mellitus) symptoms including increased urination, thirst, weight loss, fatigue, nausea, vomiting, skin infections, and blurred vision. Causes and diagnosis information is provided in the information.
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