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Sample

Indication

Pathophysiology

  1. Lipids are synthesized in the liver and intestine then transported to various tissue for their metabolic function.
    1. These are insoluble, so these are transported as macromolecules complexes called lipoproteins.
    2. Lipoprotein simple structure is explained in the following diagram.

    1. 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. Fats are absorbed from the intestine as chylomicrons which transports the dietary fats to the muscles and the adipose tissue.

  1. LDL:
  2. This is the Cholesterol that is carried in the circulation by LDL (Low-density lipoprotein).
  3. LDL has a longer half-life of 3 to 4 days than its precursors of VLDL.
  4. LDL is produced by the liver and intestinal mucosal cells.
  5. LDL catabolism takes place in the liver and peripheral tissue.

  1. LDL consists of :
    1. Cholesterol 13%
    2. Cholesterol esters 39%
    3. Triglycerides 11%
    4. Phospholipids 17%
    5. Protein 20%
      1. Another source (Teitz Fundamental of Clinical Chemistry):
        1. Cholesterol 8%
        2. Cholesterol esters 42%
        3. Triglycerides 6%
        4. Phospholipids 22%
        5. Apoproteins 22%

  1. Functions of LDL:
    1. This is called bad cholesterol.
    2. Most of the cholesterol carried by the LDL is deposited in the lining of the blood vessels.
    3. LDL increases the risk of atherosclerosis in the coronary arteries (High level of LDL is atherogenic).
    4. LDL also causes peripheral vascular disease.

  1. LDL level can be lowered by diet, exercise, and statin.
  2. LDL is mainly metabolized in the liver.

Normal 

Source 1

LDL-Cholesterol:

Age  Male mg/dL  Female mg/dL
 Cord blood 20 to 56 21 to 58 
 5 to 9 year 63 to 129 68 to 140
 10 to 14 year 64 to 133  68 to 136 
 15 to 19 year 62 to 130 59 to 137 
 20 to 24 year 66 to 147  57 to 159
 25 to 29 year   70 to 165 71 to 164 
30 to 34 year 78 to 185 70 to 156
35 to 39 year 81 to 189 75 to 172
40 to 44 year 87 to 186 74 to 174
45 to 49 year 97 to 202 79 to 186
50 to 54 year 89 to 197 88 to 201
55 to 59 year 88 to 203 89 to 210
60 to 64 year 83 to 210 100 to 224
65 to 69 year 98 to 210 92 to 221
>70 year 88 to 186 96 to 206

The risk of coronary artery disease:

Another source

Calculation of LDL

The LDL can be calculated by the following formula:

NOTE: These formulas only help if the fasting triglycerides value is < 400 mg/ dl.

Significance

Increased LDL values are seen in:

  1. Familial hyperlipidemia type 2.
  2. Familial hypercholesterolemia.
  3. Glycogen storage diseases.
  4. Secondary causes are :
    1. Hypothyroidism.
    2. Nephrotic syndrome.
    3. Multiple myelomas.
    4. Dysglobulinemia.
    5. Liver disease with obstruction.
    6. Diabetes mellitus.
    7. Chronic renal failure.
    8. Diet high in cholesterol and saturated fats.
    9. Alcohol intake.
    10. Hepatoma.

Decreased values seen in:

  1. Hypolipoproteinemia.
  2. Hyperthyroidism.
  3. Hyperlipoproteinemia type 1.
  4. Chronic anemias.
  5. Hepatocellular diseases.
  6. Chronic pulmonary disease.
  7. Reye’s syndrome.
  8. Acute stress like a burn.
  9. Inflammatory joint disease.

NCEP classification of total cholesterol and LDL in adults

Category Total cholesterol LDL-cholesterol
Desirable < 200 < 130
Borderline 200 to 239 130 to 160
High > 240 > 160

Adult treatment panel III (ATP III) classification of cholesterol:

  1. Desirable  level  =  < 200 mg/dL
  2. Borderline level  =  200 to 239 mg /dL
  3. High level           =  > 240 mg/ dL.
  1. Optimal level          = < 100 mg/ dL.
  2. Near optimal level   = 10 to 129 mg/ dL.
  3. Border line level      =  130 to 159 mg/ dL.
  4. High level                =  160 to 189 mg / DL.
  5. Very high level        =  > 190 mg/ dL.
  1. Low level               = < 40 mg / dL.
  2. High level              =  > 60 mg / dL.

ATP III (Adult treatment panel) recommendations for LDL

Risk Group Risk Factors  Target or desirable level of LDL
Presence of coronary heart disease (CHD) or CHD-equivalent If there is coronary heart disease,  diabetes, noncoronary atherosclerotic vascular disease,  <100 mg/dL
 2 or more major risk factors  Major risk factors are: Hypertension (140/90), smoking, F/O premature coronary heart disease, HDL <40  <130 
 >2 major risk factors  Above are the major risk factors <160 mg/dL 


 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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