| High Density Lipoprotein |
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| lipid disorders | |
| cardiology | |
| lipoproteins | |
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Because HDL can remove cholesterol from Atheroma within arteries, and transport it back to the Liver for excretion or re-utilization, they are seen as "good" lipoproteins. When measuring cholesterol, any contained in HDL particles serves as protection to the body's cardiovascular health. (In contrast to "bad" LDL cholesterol.) HDL are the smallest of the lipoproteins. They are the densest because they contain the highest proportion of , the original method developed in the 1970s or newer NMR Spectroscopy methods, developed in the 1990s . Men tend to have noticeably lower HDL levels, with smaller size and lower cholesterol content, than women. Men also have an increased incidence of Atherosclerotic heart disease. Epidemiological studies have shown that high concentrations of HDL (over 60 mg/dL) have protective value against Cardiovascular Disease s (such as ischemic Stroke and Myocardial Infarction ). Low concentrations of HDL (below 40 mg/dL for men, below 50 mg/dL for women) are a positive risk factor for these Atherosclerotic diseases. HDL particles are not inherently protective. It is only the HDL particles which become the largest, i.e. are actually picking up and carrying cholesterol, which are protective. There is no reliable relationship between total HDL and large HDL, and more sophisticated analyses which actually measure large HDL, not just total, correlate much better with clinical outcomes. In the Stress Response , Serum Amyloid A , which is one of the Acute Phase Proteins and an apolipoprotein, is under the stimulation of Cytokine s ( IL-1 , IL-6 ) and Cortisol produced in the liver and carried to the damaged tissue incorporated into HDL particles. At the inflammation site, it attracts and activates leukocytes. In chronic inflammations, its deposition in the tissues manifests itself as Amyloidosis . RECOMMENDED RANGE The American Heart Association , NIH and NCEP provides a set of guidelines for male fasting HDL levels and risk for Heart Disease . More sophisticated laboratory methods measure not just the total HDL but also the range of HDL particles, typically divided into 5 groups by size, instead of just the total HDL concentration as listed above. The largest two groups (most functional) of HDL particles have the most protective effects. The two groups of smallest particles reflect HDL particles which are not actively transporting cholesterol, thus not protective. CITATIONS SEE ALSO REFERENCES ''See also'': Cholesterol , Low Density Lipoprotein |
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