While 25% of the cholesterol in our body is taken directly in the form of cholesterol with food, 75% is formed by producing from other molecules in our body. Cholesterol produced in our body is produced from acetyl CoA, which is one of the products formed after the breakdown of glucose in the cells and the release of energy. The main sites of synthesis are the liver and intestinal wall. About 90% of endogenous plasma cholesterol is synthesized in these tissues. Approximately 75% of blood cholesterol is endogenous and 25% is exogenous, that is, from food.
Cholesterol is one of the vital substances for our body. It is of great importance in our body both as a building material and as a raw material for many steroid compounds. Cholesterol is a very important building block in the membrane structures of all cells and intracellular organelles. For example, bile acids, all steroid hormones produced in the adrenal gland and gonads, and vitamin D are synthesized from cholesterol.
High cholesterol level is the condition of having too much cholesterol in the blood. It is mainly caused by eating fatty foods, not getting enough exercise, being overweight, smoking and drinking alcohol. It can also run in families genetically. You can find detailed information about high cholesterol levels in our hyperlipidemia article.
Lipids are insoluble in plasma. Circulating lipids are transported to lipid stores within lipoproteins for steroid hormone production and bile acid production. In addition to lipid transport, lipoproteins are also responsible for innate immunity against microorganisms that enter the body. Plasma lipoproteins are divided into 5 main classes according to their density. These:
- chylomicrons
- Very Low-Density Lipoprotein (VLDL) (Very Low-Density Lipoprotein)
- Intermediate density lipoprotein (IDL)
- Low-density lipoprotein (LDL) (Low-Density Lipoprotein)
- High-density lipoprotein (HDL) (High-Density Lipoprotein)
By measuring the blood levels of these lipoproteins, it is possible to interpret the cholesterol levels in the blood.
LDL: Carries cholesterol from the liver to all body cells.
HDL: Collects excess cholesterol in the blood and brings it to the liver.
Total cholesterol is the sum of LDL, HDL, and VLDL. Triglyceride is another fatty substance circulating in the blood, and its high level increases the risk of heart attack and stroke.
LDL is a lipoprotein that carries low-density cholesterol in the blood to all body cells. The increase in this lipoprotein in the blood indicates the intensity of the process of transporting low-density cholesterol into cells.
Why is LDL cholesterol risky?
High amounts of LDL cholesterol in the blood are deposited on the walls of blood vessels. Especially the vessels feeding the heart and brain are affected much more by this situation. Cholesterol deposits on the vessel wall combine with other base substances and some blood cells and residues to form plaques on the vessel wall. The formation of cholesterol plaques in the vessel wall is called arteriosclerosis or atherosclerosis.
The plaque accumulating on the vessel wall multiplies over time, grows into the vessel and narrows the vessel over time. When the vessel narrows, it cannot bring enough blood to the heart muscles it feeds. Damages occur in organs that do not receive blood. If this occurs in the cerebral vessels, it can cause paralysis. Each 10 mg/dl increase in LDL cholesterol values increases the risk of heart attack by approximately 20%.
HDL cholesterol has the opposite effect.
What are normal levels of LDL cholesterol?
The generally accepted normal values of LDL cholesterol are:
- Normal: less than 130 mg/dl
- Borderline high: 130-159 mg/dl
- High: 160 mg/dl and above
LDL cholesterol in children:
- < 110 mg/dl acceptable value
- Intermediate values of 110 – 129 mg/dl
- Values of 130 mg/dl or more are considered high.
Most of the drugs used to reduce cholesterol levels try to reduce the level of LDL cholesterol in the blood. In particular, statins reduce the production of cholesterol in the liver and reduce the level of cholesterol (LDL) carried by LDL lipoproteins in the blood.
Reducing LDL cholesterol levels is very important in risky patients. While it is aimed to reduce LDL cholesterol levels below 160 mg/dl in patients who do not have any other disease and only have high cholesterol, it is aimed to have LDL-C value below 100 mg/dl in patients with diabetes or coronary heart disease.