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Sample

Precautions

  1. Don't use oxalate, fluoride, citrate or heparin for the collection of the blood.
  2. HDL values are age and sex-related.
  3. HDL value is increased in Hypothyroidism and decreased in Hyperthyroidism.
  4. Drugs that increase the value are oral contraceptives, aspirin, phenothiazine, steroids, and sulphonamides.
  5. Smoking and alcohol decrease the HDL value.

Purpose of the test

Pathophysiology

  1. Lipoproteins are insoluble so these are transported in the plasma as a macromolecular complex.
    1. Lipoproteins are sphericle particle with:
      1. Nonpolar lipids are triglycerides and free cholesterol.
      2. Polar lipids are phospholipids and free cholesterol.

      1. Lipoprotein is classified by electrophoresis on the basis of their physical and chemical structure as follows:
        1. Chylomicron. (These are primarily triglycerides).
        2. LDL. (Beta-lipoprotein These are primarily cholesterol).
        3. VLDL. (Pre-beta - lipoprotein These are mainly triglycerides).
        4. HDL. (Alpha – lipoprotein, These are mainly protein with the small amount of cholesterol)
      2. The outer covering lipoproteins are called Apoprotein and these are classified into:
        1. Apo-1.
        2. Apo-II.
        3. Apo- B.
        4. Apo-D.
        5. Apo-E.
          1. Apolipoproteins are a hydrophilic component of the lipoproteins.
          2. While lipids like cholesterol and triglycerides are hydrophobic and need to be placed in water-soluble micellar structures (Apolipoproteins)  in order to be transported in the plasma.

 

  1. In the case of endogenous pathways, the lipoproteins are synthesized in the liver from carbohydrates and fats.

  1. High-density lipoprotein cholesterol is produced by the liver and intestine.
    1. This can be separated by electrophoresis and ultracentrifugation.
    2. HDL composed of phospholipids and apolipoprotein (Apo A-1 and Apo - A-II), these are almost 90% of the total protein.
    3. The ratio of Apo - A-1 to Apo - A-11 is ∼ 3:1 by weight.
    4. The dominant Apoprotein is Apo-A I (67%) and it is followed by A II, C, and E.
    5. This may be responsible for the transport of dietary cholesterol.
    6. HDL plays a role in the transportation of cholesterol to the liver from the tissue where it is excreted in the bile.
      1. HDL transport cholesterol to the liver where cholesterol serves as the precursor of the bile acids or part of VLDL component.
      2. While lipoproteins transport cholesterol, triglycerides, and other insoluble fats.
  2. HDL (Composition) consists of:
    1. Cholesterol 6%
    2. Cholesterol ester 13%
    3. Triglycerides 3%
    4. Phospholipids 28%
    5. Protein  50%
      1. HDL has very few triglycerides.
      2. There is a high percentage of proteins, phospholipids, and cholesterol.

  1. The ratio of esterified and free cholesterol is 3:1.
  2. Decreased level of HDL is atherogenic.
    1. HDL Raised level protect against atherosclerosis by removing the cholesterol from the arteries and taking it to the liver.
    2. HDL and LDL may combine to maintain cellular Cholesterol balance through the mechanism of LDL moving cholesterol into the arteries and HDL removing it from the arteries.
    3. HDL-C is good cholesterol and is proportional to coronary artery disease (CAD) risk.

  1. When there is high cholesterol with a high level of HDL, the treatment is not indicated.
  2. Functions of HDL: 
    1. HDL are the carriers of cholesterol from the peripheral tissue.
    2. From peripheral tissue, HDL carries cholesterol to liver for excretion in the bile known as reverse cholesterol transport.
    3. HDL has a protective role by preventing cellular uptake of cholesterol and lipids.
    4. HDL protects against cardiovascular diseases.

Table showing HDL and its relationship with coronary heart disease

Risk of heart disease Male Female
Low 60 mg/dL HDL 70 mg/dL HDL
Moderate 45 mg/dL HDL 55 mg/dL HDL
High 25 mg/dL HDL 35 mg/dL HDL
  1. Total cholesterol / HDL-cholesterol ratio is very important to know the risk of coronary heart disease.
    1. A high ratio is associated with increased risk. 
    2. The normal ratio should be at least 5:1 and the best is 3:1. 

 Total cholesterol / HDL-cholesterol Ratio Risk for Coronary disease

Risk  Women  Men
Below average 3.3 3.4
Average 4.4 5.0
Above average X 2 times 7.0 9.6
Above average X 3 times 11.0 23.4                       


Normal

Source 1

HDL-Cholesterol

 Age  Male mg/dL  Female mg/dL
 Cord blood 6 to 53  13 to 56 
 5 to 9 year 38 to 75   36 to 73
 10 to 14 year 37 to 74  37 to 70 
 15 to 19 year 30 to 63  35 to 74 
 20 to 24 year 30 to 63  33 to 79
 25 to 29 year   31 to 63 37 to 83 
30 to 34 year 28 to 63 36 to 77
35 to 39 year 29 to 62 34 to 82
40 to 44 year 27 to 67 34 to 88
45 to 49 year 30 to 64 34 to 87
50 to 54 year 28 to 63 37 to 92
55 to 59 year 28 to 71 37 to 91
60 to 64 year 30 to 74 38 to 92
65 to 69 year 30 to 75 35 to 96
>70 year 31 to 75 33 to 92

Source 2

HDL

Another source

HDL

Abnormal values of HDL:

  1. <25 mg/dl             =  Coronary heart disease risk is 2 times and this is a dangerous level.
  2. 26  to 35 mg/dl    =  The risk is 1.5 times. This is a high-risk group.
  3. 36  to  44 mg/dl   = The risk is 1.2 times. This is a moderate risk group.
  4. 45 to 59 mg/dl     = This is average risk group.
  5. Above 60 mg/dl  = Below average risk group.
  6. Critical values:
    1. Male = less than 35 mg/dl.
    2. Female = less than 40 mg/dl.

Increased HDL-C value seen in:

  1. A chronic liver disease like cirrhosis, hepatitis, and alcoholism.
  2. Long-term vigorous exercises.
  3. Familial hyper- alpha-lipoproteinemia.
  4. The increased level may be due to some drugs.
    1. Estrogen therapy.
    2. Moderate intake of alcohol.
    3. Insulin therapy.

Decreased HDL-C values seen in:

  1. Poorly controlled diabetes
  2. Cholestasis.
  3. Chronic renal failure, uremia, and nephrotic syndrome.
  4. Hypertriglyceridemia.
  5. Familial hypo-alpha-lipoproteinemia.
  6. alpha and beta – lipoproteinemia.
  7. The decreased level may also be seen in some of the drugs.
    1. Steroids.
    2. Antihypertensive drugs.
    3. Diuretics.
    4. Beta-blockers.
    5. Thiazide.

Table showing the summary of characteristics of the lipoproteins

Characteristics Chylomicron HDL LDL VLDL
PLasma appearance Creamy layer, slightly turbid Clear Clear, or yellow-orange tint Turbid to opaque
Size (diameter nm) >70.0 4 to 10 19.6 to 22.7 25 to 70
Electrophoretic mobility Origin α - region β - region Pre - β region
Molecular weight  0.4 to 30 x 109 3.6 x 109 2.75 x 109 5 to 10 x 109
Synthesized in (Tissue of origin) Intestine Intestine and liver  Intravascular Liver and intestine 
Composition by weight in %        
                     Cholesterol esterified 5 38 49 11 to 14
                    Cholesterol unesterified 2 10  13 5 to 8 
                    Triglycerides 84 9 11 44 to 60
                    Phospholipids 7 22 27 20 to 23
                    Proteins 2 21 23 4 to 11
Triglycerides Markedly raised Normal Normal/ Raised Moderately to Markedly raised
Clinical significance of Pancreatitis and acute abdomen Decreased risk of CAD Increased risk of CAD Increased risk of CAD
Functions Transport dietary lipids to tissue Carry cholesterol from tissue to liver Carries cholesterol to tissue Transport endogenous TG from liver to adipose tissue

Possible References Used

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