In order to understand why we measure your ‘cholesterol’ and what it means to your health you need to understand what this stuff is.
Cholesterol is essential for your health. In fact, there is no such thing as “good cholesterol” nor “bad cholesterol.” All cholesterol is the same. Cholesterol is actually only a component of lipoproteins.
There are 3 pathways for lipoprotein transport & metabolism:
- Endogenous pathway – this is the cholesterol you make in your body
- Exogenous pathway – this is the cholesterol you absorb from your diet
- HDL mediated transport (formerly known as ‘reverse cholesterol transport’) –
Lipoproteins are important for transporting
- triglycerides (primarily to muscle and fat tissue)
- phospholipids (to every cell in the body)
- cholesterol (for the formation of Vit D, hormones, cell membranes, etc)
- return unneeded cholesterol back to the liver and intestine
Atherogenic particles are those that suggest higher risk for the development of plaques.
Low-Density Lipoproteins (LDL) – often inappropriately referred to as “Bad Cholesterol.” LDL molecules are essentially left-over particles from VLDL and IDL lipolysis (where triglycerides are removed). These LDL molecules have a protein on them called apoB which binds to LDL receptors in the liver.
The cholesterol in the LDL molecules is taken into the hepatocytes (liver cells) once they bind to the LDL receptor. This cholesterol contributes to the ‘cholesterol pool’ within the liver. There is a negative feedback system in this cholesterol pool. In other words when the cholesterol pool is low the LDL receptors increase in an attempt to increase the liver’s cholesterol pool. When the hepatic cholesterol pool is high the LDL receptors decrease to try to lower the pool.
The amount of LDL receptors present also dictates the amount of LDL in circulation. Low levels of LDL receptors increase the amount of LDL particles in circulation because the simply don’t get cleared from the blood quickly.
LDL can be calculated via the “Friedewald Equation” or directly measured. The Friedewald Equation takes HDL, TC, and TGs into account. Since TGs are affected by what you ate that day you would be required to be fasting for this lab. Fasting has no effect on directly measured LDL cholesterol.
LDL is the primary carrier of serum cholesterol and generally considered a major contributor to atherosclerotic plaque. According to the National Cholesterol Education Program (NCEP) Adult Treatment Panel III (ATP III) the treatment for each patient should be guided by their absolute risk for cardiovascular disease. Age, blood pressure, smoking, and premature family history of cardiovascular disease all contribute to the absolute risk.
ApoB – This is the protein associated with LDL molecules. ApoB is associated with chylomicrons, VLDL, IDL, LDL, and Lp(a). There is 1 molecule of apoB for each molecule of chylomicron, VLDL, IDL, LDL, and Lp(a).