How to look at your cholesterol profile?

Elevated cholesterol level (hyperlipidaemia) is an important cardiovascular risk factor. Most of us would go to doctor or “pathology labs” requesting to check our cholesterol (lipid) levels. Patients fast for at least 12 hours (excluding medications and clear fluids) before blood taking. Hence, Fasting Serum Lipid (FSL) or Fasting Lipid Profile (FLP). There would be at least 4 parameters that we look at. Three of them are cholesterol-bound-protein (lipoproteins); Total Cholesterol (TC), High Density Lipoprotein (HDL) and Low Density Lipoproteins (LDL). The final parameter would be Triglyserides (TG).

Lipoprotein is produced by liver and excreted into the bloodstream. These lipoproteins have essentially two main components, lipid and protein. Immediately after being released in the blood, these lipoproteins have low lipid but high protein content. Hence it is called HDL. As these lipoprotein moves around the circulation, it absorbs lipids or cholesterol. This will increase the quantity of lipid in these lipoproteins. Hence it is called LDL. LDL then is reabsorbed by liver. Cholesterol then is excreted or released as bile.

TG is actually fatty acid which comes from our diet. The excessive energy which is not used up by our body is converted into TG which then stored in fat cells.

pathways of lipids..

So we actually measure the lipoprotein levels as a reflection of our cholesterol profile. This is because free cholesterol is absent from our blood. It is a hydrophobic molecule.

HDL and LDL have low and high lipid content respectively. Hence increased HDL level is a good sign as it acts as a scavenger to lipid. Increase LDL however is a sign that there is too much cholesterol in our circulation. The higher the LDL, the high the risk of cardiovascular event (eg stroke or heart attack). The FSL measurements are given in either µmol/L or mmol/L.

Of these 4 parameters, LDL has the strongest link to cardiovascular disease. Numerous studies have shown that the lower the LDL level the lower the risk of cardiovascular event. TC, HDL and TG levels are not as strong predictor of cardiovascular events.

These measurements should take into account the patient profile too. Each patient has his or her own target cholesterol levels. The high the risk, the lower the LDL level should be.

LDL targets

High Risk Patients (previous heart attack / type II DM) less than 2.0mmol/l

Intermediate Risk Patients (hypertension) less than 2.5mmol/l

Low Risk Patients less than 3.0mmol/l

Until these targets are reached, only then one should consider modifying the other lipid profile parameters, namely TG and HDL.