Cholesterol is a component (a lipid or fat) that circulates in the bloodstream which the body uses to construct cells and produce certain substances that it needs. In this respect, its presence is both good and necessary. However, hypercholesterolaemia, or an excessive level or amount of cholesterol in the blood, can be harmful because it causes atheromatous plaques to deposit in the arteries (atherosclerosis). Therefore, it predisposes the development of cardiovascular diseases such as heart attacks, strokes or an insufficient blood supply to the limbs.
Total cholesterol in blood of less than 200 mg/dL is considered an "ideal" value and hypercholesterolaemia is generally used to refer to levels of above 240–250 mg/dL.
These cholesterol levels are taken as a reference point for evaluating aspects of cardiovascular health or prompting the need to introduce measures to reduce them. They should not be confused with each patient’s desirable individual target values, which depend on their specific risk factors, age and any other diseases they may have.
What is cholesterol?
Cholesterol is a type of fat (a lipid) that is essential for the construction of cell membranes, it is a precursor for certain hormones and bile acids (the bile), besides being used in other vital processes.
Cholesterol from the body comes from the foods that are ingested and the cholesterol that the liver is capable of developing on its own. The liver acts as a cholesterol service station, serves as a deposit, and it is the origin and destination of cholesterol that goes and comes from the tissues of the body and the arteries in a constant manner. However, cholesterol does not circulate freely through the blood. As it is a fat it cannot circulate in an aqueous medium, just like oil does not mix with water. Therefore, cholesterol needs to be transported so it is packaged inside small spheres called lipoproteins that distribute it throughout the body. Although in reality there is only one type of cholesterol, "good" cholesterol and "bad" cholesterol are usually referred to. This classification refers to the lipoprotein that transports it.
LDL or low-density lipoprotein. It carries the so-called "bad cholesterol" because when it is directed from the liver to the tissues it also deposits in the walls of the arteries.
HDL or high-density lipoprotein. It carries the so-called "good cholesterol" because it distributes cholesterol from the tissues and arteries (which helps clean them) to the liver where it is metabolised.
In a normal situation, the body maintains cholesterol levels in a balanced equilibrium between production (both biosynthesised and absorbed from food) and elimination through the digestive tract. When there is little quantity in the feed, internal production increases and elimination is reduced. In other words, the body is well prepared to live with very little cholesterol, but it is not very well prepared to destroy or eliminate it. Therefore, when the body receives too much cholesterol because of an unhealthy diet, it gradually accumulates and deposits in the arteries.
Cholesterol circulating inside LDL lipoproteins (bad cholesterol) filters from the blood into the wall of the arteries. The body interprets these cholesterol deposits as harmful and, in its attempt to eliminate them, it initiates an inflammatory response which subsequently transforms the deposits into atheromatous plaques (cholesterol plaques). These plaques are responsible for cardiovascular diseases.
Types of Hypercholesterolaemia
Hypercholesterolaemia is classified based on its:
As secondary hypercholesterolaemia. Are producedwhen it is caused by an underlying disease (e.g. diabetes, obesity, low thyroid hormone levels, certain kidney and liver diseases, amongst others); circumstances (pregnancy); a medication (some acne tablets, contraceptives or cortisone, for example); or a poor diet (high in fats, sugar, alcohol). All these situations are primarily causes high cholesterol levels.
As primary hypercholesterolaemia. When it is essentially due to an inherited defect in the genes which control the body’s cholesterol levels. Some examples are familial hypercholesterolaemia, familial combined hyperlipidaemia or polygenic hypercholesterolaemia. In many cases people with primary hypercholesterolaemia also have secondary causes that contribute to increased cholesterol levels and make it even harder to control their condition.
Presentation. Situations may occur in which only high cholesterol levels (pure hypercholesterolaemia), or at other times these are also associated with an increase in triglycerides (hyperlipidemia or mixed dyslipidemia) or low amounts of good cholesterol (HDL).
How many people are affected by Hypercholesterolaemia?
It is hard to establish the prevalence of cholesterol conditions. High cholesterol levels vary depending on age, sex, racial and ethnic origins or even a person’s cultural or healthcare environment. In general terms, if we consider the “ideal levels” for cholesterol, it is estimated that 1 in 2 people are outside this range. Around 5%–20% of the population have cholesterol levels above 240–250 mg/dL; familial hypercholesterolaemia affects 1 in every 250 people and around 50%–80% of them are unaware of their condition. While approximately 1%–5% of the population may have familial combined hyperlipidaemia.