What are the Ideal Cholesterol Levels?

Total cholesterol is the sum of cholesterol in all lipoproteins in the blood. The total cholesterol level of a population depends mainly on genetic factors and lifestyle. Total cholesterol includes free cholesterol and cholesterol esters, and the liver is the main organ for synthesis and storage. Cholesterol is an important raw material for the synthesis of physiologically active substances such as adrenocortical hormones, sex hormones, bile acids and vitamin D. It is also the main component of the cell membrane. Its serum concentration can be used as an indicator of lipid metabolism. Experts at home and abroad recommend that the ideal cholesterol value for adults is <5.2mmol / L. ^[1]

Total cholesterol refers to the cholesterol contained in various lipoproteins in the serum, that is, the sum of bound cholesterol and free cholesterol. Since cholesterol in serum is basically present in lipoproteins in a bound state, it mainly represents bound cholesterol. Because it cannot reflect the amount of various lipoproteins, it cannot accurately reflect the amount of high-density lipoprotein cholesterol and low-density lipoprotein cholesterol, so it cannot be used as a judgement of the magnitude of atherosclerosis risk alone Accurate indicators. ^[2]

(1) Diet : As we all know, many animal foods contain cholesterol, and the content of certain organs is quite high, such as the brain, kidneys, liver, lungs, fat, egg yolk, crab yellow, shrimp, fish roe and so on. Generally, 500-800 mg of cholesterol is absorbed from the diet per person per day.

(2) Internal self-synthesis: Except the brain, most tissues of the human body have the ability to synthesize cholesterol, especially the liver, which accounts for 70% -80% of the total cholesterol synthesis in the body. Followed by the small intestine, accounting for about 10%, skin, adrenal cortex, gonads, etc. are also important sites for cholesterol synthesis, and the brain's ability to synthesize cholesterol is very low. Sugar, fat and protein are all ingredients for the synthesis of cholesterol. The human body can synthesize 1000-2000 milligrams of cholesterol every day. When the intake is high, the synthesis is low, and when the intake is low, the synthesis is high. Excess cholesterol is converted into bile acids, which are excreted in the urine and feces. Cholesterol in the body is mainly synthesized from organic sources in the body and produces 1-2 grams per day, which is higher than the absorption of cholesterol in food under ordinary dietary conditions.

It can be seen that the sources of cholesterol in the human body are divided into exogenous and endogenous. Exogenous cholesterol comes from foods rich in cholesterol; endogenous cholesterol is synthesized by the body itself, the main place is in the liver.

In the human body, lipid substances are mainly divided into two categories. Fats (mainly triglycerides) are the most abundant lipids in the human body, and are a major source of energy in the body; the other is called lipids, which are the basic components of biofilms and account for about 5% of body weight. In addition to glycolipids, there is a very important one called cholesterol.

Cholesterol is also called cholesterol, a derivative of cyclopentane polyhydrophenanthrene. Cholesterol is widely present in animals, especially in brain and nervous tissues, and is also high in kidney, spleen, skin, liver and bile. Its solubility is similar to that of fat. It is insoluble in water and easily soluble in solvents such as ether and chloroform. Cholesterol is an indispensable and important substance for animal tissue cells. It is not only involved in the formation of cell membranes, but also a raw material for the synthesis of bile acids, vitamin D and steroid hormones.

The total amount of cholesterol in the human body accounts for about 0.2% of body weight, bone contains about 10 mg, skeletal muscle contains about 100 mg, viscera is mostly between 150-250 mg, and liver and skin are slightly higher, about 300 mg. The highest content in brain and nervous tissues, about 2 grams per 100 grams of tissue, the total amount of which accounts for about 1/4 of the body's total low density cholesterol and high density cholesterol functions. Low density cholesterol actually refers to low density lipoprotein. In cholesterol, it can reflect the amount of low density lipoprotein. Low-density lipoprotein is converted from intermediate-density lipoprotein in the liver. The liver can also directly synthesize and secrete a small amount of low-density cholesterol. Its main function is to transport cholesterol to extrahepatic tissue cells to meet their needs for cholesterol.

LDL is the primary atherogenic lipoprotein of all serum lipoproteins. HDL actually refers to cholesterol in HDL, which can reflect the amount of HDL in serum.

High density lipoprotein is mainly synthesized by the liver and small intestine, and is the smallest volume of lipoproteins. Its main function is to transport excess cholesterol in extrahepatic tissues to the liver for metabolism to prevent cholesterol from accumulating in these tissues too much. Modern research has confirmed that high-density cholesterol has the effect of preventing atherosclerosis and reducing the mortality of coronary heart disease. ^[3]

Adult appropriate level: 2.83 ~ 5.20mmol / L (110 ~ 200mg / dl)

Critical value: 5.17 ~ 6.45mmol / L (200 ~ 250mg / dl)

Hypercholesterolemia:> 6.45mmol / L (> 250mg / dl) ^[2]

1. Cholesterol specimens should be collected for 12 to 14 hours after fasting. They should not drink alcohol within 24 hours and avoid the effects of taking related drugs. Serum was separated within 2 hours, stable at 4 ° C ~ 25 ° C for 6 days, and stable at -20 ° C for 4 months.

2. When bilirubin> 171 mol / L, there is a significant negative interference to the reaction results.

3. It will cause positive interference when hemolysis, but the interference is negligible when Hb is below 1g / L.

4. High blood uric acid can also cause negative interference.

5. A large number of reducing drugs, such as vitamin C, phenanthramine, promethazine hydrochloride, and compound salvia miltiorrhiza, etc., can also interfere with the reaction to make the results low.

1. Pathologically elevated. Hyperlipoproteinemia, atherosclerosis, diabetes, hypothyroidism, obstructive jaundice, nephrotic syndrome.

2. Pathological decrease. Hyperthyroidism, severe anemia, acute infection, wasting disease, liver disease. ^[2]