What is LDL cholesterol?
LDL cholesterol is a lipoprotein, i.e. a compound of fats (such as cholesterol) and proteins. Only in such a compound can water-insoluble substances such as cholesterol esters be transported in the predominantly aqueous blood. Other lipoproteins include HDL cholesterol and VLDL cholesterol. The latter is the precursor to LDL.
The liver initially produces VLDL (very low density lipoproteins), which is loaded with cholesterol and other fats (triglycerides). Through the breakdown of triglycerides by certain enzymes and changes in the structure of the lipoprotein, LDL cholesterol is produced via an intermediate stage (IDL). Its task is to transport cholesterol from the liver to the body’s cells. These cells need the cholesterol to build the cell membrane and to produce various hormones (such as oestrogen).
Normally, the cells regulate the uptake of cholesterol by no longer presenting receptors for its uptake on their surface when there is an excess. At the same time, cholesterol production in the liver is inhibited if the cholesterol level in the blood is sufficient.
Familial hypercholesterolemia, on the other hand, is caused by a defect in the LDL receptor. Those affected have little or no functional LDL receptor structures. As a result, atherosclerosis develops in childhood and secondary symptoms such as coronary heart disease develop much earlier than usual.
When is LDL cholesterol determined?
The LDL cholesterol value is particularly important if the doctor wants to assess the risk of atherosclerosis. This plays a particular role if patients are already suffering from signs of cardiovascular disease such as coronary heart disease. The LDL value is also determined if a lipometabolic disorder is suspected or to monitor the success of a lipid-lowering therapy (e.g. diet or medication).
Blood values – LDL
To determine the LDL cholesterol, the doctor takes blood samples from the patient. The patient should be fasting for the first test, but should have refrained from eating excessively fatty meals and drinking alcohol, especially in the days beforehand. Nowadays, many laboratories can also determine LDL regardless of whether the patient is fasting or not. Therefore, patients no longer have to be fasting for follow-up checks.
However, if there are risk factors for cardiovascular disease, the LDL cholesterol should be even lower, namely less than 100 mg/dl (or at least the elevated LDL should be reduced by at least half). If patients already suffer from coronary heart disease, for example, experts recommend an LDL cholesterol of less than 70 mg/dl.
The LDL/HDL ratio can also be helpful in assessing a patient’s risk of arteriosclerosis: The more LDL cholesterol and the less HDL cholesterol someone has, the higher the quotient, and vice versa.
In people who have no other risk factors for arteriosclerosis (such as high blood pressure), the LDL/HDL ratio should be below four. In contrast, a ratio below three is recommended for people with such other risk factors and a ratio below two for people who already have arteriosclerosis, for example.
The LDL/HDL ratio has now lost some of its significance when it comes to estimating cardiovascular risk. Apparently, extremely high levels of “good” HDL cholesterol (above approx. 90 mg/dl) pose an increased risk of arteriosclerosis. The following therefore does not apply to HDL cholesterol: the more, the better.
LDL cholesterol in children and adolescents
In young children, the following LDL cholesterol guideline values are considered acceptable, depending on age:
|
LDL value |
|
|
1-3 years |
< 90 mg/dl |
|
4-7 years |
< 100 mg/dl |
|
8-19 years |
< 110 mg/dl |
The following also applies to older children and adolescents: LDL cholesterol levels fluctuate more than in adults. It changes with physical development. LDL levels rise particularly in the first three years and towards the end of puberty. Girls generally have slightly more LDL cholesterol in their blood than boys of the same age.
When is LDL cholesterol too low?
LDL cholesterol is only low in very rare cases. Studies have also shown that even at very low levels, there are still enough reserves for hormone production, for example. The cause of a low level can be malnutrition, although this is very rare in industrialized nations. Other possible reasons for low LDL cholesterol (or at least associated diseases) are
- Metabolic disorders
- Serious illnesses (cancer, serious infections)
- Overactive thyroid gland (hyperthyroidism)
- Liver weakness
- operations
- Overdose of cholesterol-lowering medication
- Mental illness
When is LDL cholesterol too high?
Secondary hypercholesterolemia, on the other hand, is usually the result of an unhealthy lifestyle with too little physical activity and an increased intake of calories and fat. Other possible causes are
- Diabetes mellitus
- Underactive thyroid gland (hypothyroidism)
- Kidney dysfunction
- Chronic liver or biliary tract diseases
- Anorexia (mechanism not clear)
Pregnancy can also lead to increased LDL levels. The same applies to some medications, especially sex hormones or some HIV medications.
How can I lower LDL cholesterol?
If the LDL cholesterol is too high, there is usually a need for action. The resulting and progressive arteriosclerosis is an important risk factor for the development of other diseases: Increasing vascular occlusion means that body tissues are supplied with less and less vital blood and oxygen. The possible consequences are circulatory disorders such as coronary heart disease, which can lead to a heart attack. However, arteriosclerosis also has serious consequences in other parts of the body, such as the brain (stroke) or legs (peripheral arterial occlusive disease, PAOD).
