Understanding HDL, LDL, non-HDL Triglycerides

By Edward Pullen, MD
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Physicians talk of the lipid profile, or lipid type, while most patients want to know about their cholesterol.  We really are on the same team, looking for the same goals of reducing the risk of heart and artery disease caused by abnormal levels of the types of lipids that lead to atherosclerosis.  We just have different words we use.  The jargon physicians use can be confusing, and lipid type is a good example.  First some definitions:

Lipid: really another word for fat.  A lipid is a substance that dissolves in alcohol but not in water.  Examples of lipids are wax, oil and other fats.

Cholesterol: a specific lipid that is used for many purposes in the body including cell membranes, hormones, vitamin D production and bile production.  It consists of a sterol carbohydrate ring with specific side chains.

Lipoprotein: a particle manufactured in the liver that consists of lipids and protein that circulates in the bloodstream.

Triglyceride: molecule made up of a three carbon molecule glycerin with three long carbon chain fatty acids attached, i.e. "tri" for three + glyceride. Practically these are the fatty particles in the blood stream that did not get packaged into lipoproteins in the first pass of the blood from the gut through the liver.

HDL cholesterol: (High density lipoprotein) Think good cholesterol here. The HDL lipoprotein particle consists of more proteins which are more dense, and less lipids which are less dense, so the lipoprotein is high in density.  There are several subsets of HDL, but in general a high HDL level is good.  HDL cholesterol functions in part to remove cholesterol from places it does not belong and return it to the liver to be repackaged and better used.

LDL cholesterol: (Low density lipoprotein) Think bad cholesterol here.  A lipoprotein that is higher in lipid and lower in protein making it low density.  In general high levels of LDL cholesterol are not good, as they increase the risk of atherosclerosis and heart disease.  LDL cholesterol is the primary vehicle for carrying cholesterol in the blood stream.  When present in large amounts cholesterol is often put where it can cause harm, like on the lining of blood vessels.

CRP: (C-reactive protein or hsCPR for highly sensitive CRP) is a marker of inflammation, and is used sometimes to assess risk of heart disease when the cardiovascular risk based on the rest of the lipid measurements and the other risk factors do not lead to a clear decision on lipid management.

Non-HDL cholesterol: This is simply calculated by subtracting the HDL cholesterol level from the total cholesterol level.  non-HCL cholesterol is a secondary target for treating lipids, after the LDL goal is met.

Direct LDL: usually the LDL level is calculated using the formula:

Total Cholesterol - HDL cholesterol - Triglycerides/5 = LDL cholesterol

This formula is quite accurate except when the triglyceride level is over 400-500.  High triglyceride levels make this calculation less accurate, so in those cases a more expensive test is used to measure the LDL cholesterol directly.

Physicians use these numbers along with a patients other risk factors to decide on whether to treat them with medication for abnormal lipid measurements.  In general the more risk factors for heart disease a patient has the more likely they are to warrant medication treatment.

 

The risk factors recommended by the National Institute of Health (through the NHBLI) for this decision making include:
Table 3. Major Risk Factors (Exclusive of LDL Cholesterol) That Modify LDL Goals*

- Cigarette smoking
- Hypertension (BP ³140/90 mmHg or on antihypertensive medication)
- Low HDL cholesterol (<40 mg/dL)†
- Family history of premature CHD (CHD in male first degree relative <55 years; CHD in female first degree relative <65 years)
- Age (men ³45 years; women ³55 years)*

* In ATP III, diabetes is regarded as a CHD risk equivalent.
† HDL cholesterol ³60
(table from the NIH site)

 

The levels of cholesterol are broken down into categories:
Table 2. ATP III Classification of LDL, Total, and HDL Cholesterol (mg/dL)

LDL Cholesterol
<100	Optimal
100-129	Near optimal/above optimal
130-159	Borderline high
160-189	High
>190	Very high
Total Cholesterol
<200	Desirable
200-239	Borderline high
³240	High
HDL Cholesterol
<40	Low
>60	High

(table from the NIH site)

 

The recommendations for goal LDL cholesterol are as follows:
Three Categories of Risk that Modify LDL Cholesterol Goals

Risk Category LDL Goal (mg/dL)
CHD and CHD risk equivalents	<100
Multiple (2+) risk factors*	<130
Zero to one risk factor	<160

* Risk factors that modify the LDL goal are listed in Table 3
(from the NIH site)

 

Using these recommendations a woman age 67 who does not smoke, has a BP < 140/90 on no blood pressure medication, has an HDL cholesterol of 38, and has no coronary heart disease in her mother, father, or siblings would have 2 risk factors (age plus low HDL cholesterol) making her goal LDL <130.

Similarly a man age 40 who smokes, is on BP medication, and whose father had his first heart attack at age 50 with an HDL of 33 would have three risk factors (smoking, blood pressure and family history)  so his goal LDL cholesterol would be <130 unless his Framingham calculated risk of developing Coronary disease in the next 10 years is >20%.

Here is a link to the calculator provided by the NIH to calculate Framingham Risk: Framingham Risk Calculator

Using this calculator the 10 year risk of the man above would be 22% if his current systolic BP was 130 on medication, so he falls into the CHD equivalent category and has a goal of <100 for LDL cholesterol.

Treating LDL cholesterol is usually pretty straightforward.  We try to get patients to eat a diet low in total fat and saturated fat (primarily animal fat) to avoid trans fatty acids, and to lose weight.  If this is not adequate we usually add a medication in the statin family.  Many generic statins are available and can keep costs of treatment fairly low, and most patients tolerate statins well.  Some patients do not and red yeast rice is sometimes tolerated by those patients. It has a statin-like effect.  Statins can lower LDL cholesterol by 25-55% in most patients. If statins are not tolerated, or if you are a woman who may become pregnant (absolute contraindication to statins) then other medications are sometimes used.

Treating low HDL cholesterol is more difficult, and often slow release niacin is used for this purpose, but it is sometimes difficult to tolerate because of flushing and itching side effects.

Treating triglycerides is important if they are extremely high.  Levels >500 can put you at risk for pancreatitis, and need to be treated.  Levels between 150 and 500 are suboptimal, and are sometimes treated.

Hopefully this has been helpful in understanding your lipid profile. In general the goals for non-HCL cholesterol are the LDL goals + 30.