When a doctor orders a cholesterol test, he will often look not only at the total cholesterol but at the level of each type of cholesterol found in the blood, which includes LDL, HDL and VLDL. Depending on the form of cholesterol, it can increase a patient's risk of heart disease or lower it. This is why it is important to understand the role of lipoproteins in the body.
Lipoproteins
Lipoproteins (of which LDL is an example) are molecules that are a combination of lipids and protein. Educator's Top 15 explains that a lipoprotein contains a lipid core (mostly made up of cholesterol and triglycerides) that is surrounded by a protein and cholesterol-filled shell.
Purpose
Lipoproteins are made by the body to help transport lipids. Lipids are made up of oils, which means that they do not dissolve well in the watery environment of the blood. Lipoproteins serve as a way for lipids to be transported through the blood by wrapping them up in proteins. Thus, cholesterol and other lipids need to be put into lipoproteins to be able to be moved from the intestines to the rest of the body. Cells throughout the body need lipids for cell membranes as well as the membranes that surround some of their other structures.
Types of Lipoproteins
Although lipoproteins all have the same basic function (lipid transport), there are many different kinds. LDL is short for low-density lipoprotein, which is often considered to be "bad" cholesterol. Other examples of lipoproteins include high density lipoprotein (HDL), often refered to as "good" cholesterol; and very low density lipoprotein (VLDL). The different forms of lipoprotein tend to distribute the lipids and cholesterol to different parts of the body.
Danger of LDL
LDL is considered to be the "bad" form of cholesterol because it can deposit cholesterol in the walls of the arteries. As Lab Tests Online explains, when cholesterol gets deposited in the arteries, it can cause them to become unusually thick and hard, a condition known as atherosclerosis. This can cause the patient's blood pressure to increase and can also result in blood flow impairment in those arteries. Sometimes the atherosclerotic material can break off and travel to smaller blood vessels in the heart or brain, leading to a stroke.
Lp(a)
According to the American Heart Association, Lp(a) is a variation of LDL. High levels of Lp(a) put a patient at risk for developing heart disease. It is not understood what the function of Lp(a) is in the body or how it leads to heart disease, but it potentially interacts with some of the parts of arteries and speeds up how fast cholesterol accumulates within them.
