What are lipids?
Lipids are fat like substances, essential for the body to function. They are important in maintaining the structure of cells, for insulation and as energy stores. In excess however, they can be harmful. A lipid profile is a measure of the different types of fat in the blood. The amount of lipids within the blood can fluctuate with food intake, therefore a lipid test should be taken in the morning whilst fasted to allow the most accurate interpretation of results.
The most common lipids in the blood are cholesterol and triglycerides. They are unable to travel freely within water (insoluble), and therefore are bound to proteins in large complexes called lipoproteins to be transported within the blood e.g. LDL (low density lipoproteins) and HDL (high density lipoproteins).
When increased quantities of lipids (such as triglycerides and cholesterol) are found within the blood, this is termed dyslipidemia. This is associated with an increased risk of a number of conditions, including cardiovascular disease, stroke, high blood pressure (hypertension) and type 2 diabetes.
Total Cholesterol and Triglycerides
Cholesterol is essential to the body. It is a key component of cells, and is involved in the production of enzymes and hormones. Most of the cells within the body produce cholesterol, however the primary site for its production and breakdown is the liver. The body is able to make sufficient amounts of cholesterol for these important functions, but can also absorb cholesterol from animal produce such as dairy, meat and eggs.
Triglycerides are the most commonly found fat in our bodies. Calories that are consumed in excess are converted to triglycerides - which are stored in fat cells (adipose tissue), and can be used as an energy source when needed.
LDL cholesterol is often termed the ‘bad cholesterol’, and in excess alongside triglycerides will deposit in the blood vessels and form plaques. The formation of these plaques results in a condition called atherosclerosis, where the arteries in the body become hardened and narrowed due to plaque formation. Blood flow subsequently is restricted and this can lead to heart attacks (myocardial infarction), chest pain due to reduced oxygen to the heart (angina) and stroke.
HDL cholesterol is termed ‘good cholesterol’ as it helps remove other cholesterol from the blood and thus reduces the risk of atherosclerosis. As a consequence, low HDL levels are considered a risk factor for cardiovascular disease.
Non-HDL cholesterol is the collective name for all the "bad cholesterol" in the blood. Many people might already know LDL cholesterol as the "bad cholesterol", but there are actually other types of "bad cholesterol" in the blood as well, such as VLDL (very low density lipoprotein) and IDL (intermediate density lipoprotein). Non-HDL cholesterol, the total amount of "bad cholesterol", is therefore often regarded as a better marker for cardiovascular risk than just LDL cholesterol.
Total/HDL ratio and HDL/Total ratio
Not all cholesterol are bad. Two people with the same high total cholesterol value can have different risk for cardiovascular disease depending on the amount of HDL, the "good cholesterol" that they have. Including the Total/HDL ratio or HDL/Total ratio can therefore improve the overall assessment of lipid profile.
Why is this analysis important?
There are a number of conditions associated with a deranged lipid profile:
High blood pressure (hypertension)
Heart disease which can lead to heart attacks (myocardial infarction)
Cerebrovascular disease (plaque formation within the brain) which can lead to strokes
Type 2 Diabetes
Often individuals may have a deranged lipid profile for a number of years before developing any symptoms of the above, and early identification can allow the formulation of strategies to improve one's health.
Normal triglyceride, HDL, and LDL values change depending on the laboratory. The doctor will always evaluate the results based on several factors.
High triglyceride and LDL levels alongside decreased HDL levels can be related to a number of factors, including:
Lack of physical activity
Tobacco and/or alcohol use
High dietary intake of saturated fats and sugars
Family history of dyslipidemia
Drugs such as contraceptives, steroids, diuretics, beta-blockers, antiretrovirals
Kidney disease, polycystic ovary disease, pregnancy, hypothyroidism, liver disease
Dyslipidemia is also associated with the following:
Metabolic syndrome (30%)
Tests that include this marker
Consensus document on the management of atherogenic dyslipidemia of the Spanish Society of Arteriosclerosis. Juan F. Ascaso, Jesús Millán, Antonio Hernández-Mijares, Mariano Blasco, Ángel Brea, Ángel Díaz, Teresa Mantilla, Juan Pedro-Botet y Xavier Pintó.
Clínica e Investigación en Arteriosclerosis, 2017-03-01, Volumen 29, Número 2, Páginas 86-9
Patient education: High cholesterol and lipids (hyperlipidemia) (Beyond the Basics). Robert S Rosenson. www.uptodate.com/patients. 2018
Clinical Laboratory Science, 8th edition. Mary L Turgeon. 2020