Hello and welcome to Hopkins Family Med & Urgent Care, PLLC Blog. In this section we will be talking about the cholesterol/ lipid panel. We will be breaking down the different sections of this lipid panel to show you how to interpret your cholesterol/ lipid panel. This is the PART 2: Fat and Cholesterol- Nutrition Series.
Lipid Profile
Standard Lipid Profile consists of:
Total Cholesterol
HDL - cholesterol
Triglycerides
LDL - cholesterol
Lipid levels may be affected by the acute phase response that is associated with certain conditions such as Myocardial Infarction, surgery, trauma, or infection.
Total cholesterol, HDL-Cholesterol, and LDL-Cholesterol may decline.
Triglyceride level usually rises.
Hospitalization, even in the absence of the acute phase response has been shown to lower HDL-cholesterol levels.
For these reasons, it is preferable to delay lipoprotein analysis for one to two months after discharge.
Lipoproteins
A lipoprotein is a biochemical assembly whose primary purpose is to transport hydrophobic lipid molecules in water, as in blood plasma or other extracellular fluids
Lipoproteins are considered to be an accurate predictor of heart disease.
As part of the lipid profile, these tests are performed to identify persons at risk for developing heart disease and to monitor the response to therapy if abnormalities are found.
Lipoproteins are used as markers, indicating the levels of lipids within the bloodstream.
They are produced in the liver and, to a smaller degree, the intestines.
Binge eating can alter lipoprotein values.
The Basics:
Cholesterol screening should be performed at least once every five years in those over the age of 20.
Fasting lipid profile is recommended for screening.
Standard components of the lipid profile include the Total Cholesterol, LDL(low-density lipoprotein), HDL (good cholesterol, helps remove other forms of cholesterol in the body, carries to the liver.) and Triglycerides.
LDL- cholesterol level is calculated from the following equation
LDL= Total Cholesterol - HDL - (Triglycerides/5)
Knowledge of LDL- Cholesterol concentration is important in patients presenting with acute coronary syndrome. It contributes to the fatty build up in the arteries, and also increases the risk of a heart attack, stroke, and poor limb circulation.
Goal for a patient's LDL- cholesterol concentration is based on the patient's risk level.
There are 4 levels of risk
The patient's risk level can then be used to determine the LDL goal, as shown in the following table
Before initiating treatment, consider repeating the lipid profile for confirmation of results since there are biological and laboratory variations in lipid levels.
Test Explanation and Related Physiology
Nearly 75% of the cholesterol is bound to low-density lipoprotein and 25% is bound to high-density lipoprotein.
LDLs are most directly associated with increased risk of coronary heart disease
Cholesterol testing is usually done as a part of lipid profile testing, because by itself cholesterol is not a totally accurate predictor of heart disease.
Because the liver is required to make cholesterol, low serum cholesterol levels are indicative of severe liver diseases. Liver function complications can hinder the organ’s ability to produce or clear cholesterol.
The goal for high-risk patients, people with cardiovascular risk, is LDL < 70 mg/dL
Lowering of LDL-C levels will reduce the risk for major coronary events
Familial hyperlipidemias and hyperlipoproteinemias are often associated with high cholesterol.
Hyperlipidemias - abnormally elevated levels of any or all lipids or lipoproteins in the blood.
Hyperlipoproteinemias - results from an inability to break down lipids or fats in your body, specifically cholesterol and triglycerides
Interfering Factors
Pregnancy is usually associated with elevated cholesterol levels. High cholesterol levels during pregnancy are necessary to make steroid hormones, such as estrogen and progesterone, which are vital for carrying a pregnancy to term
Oophorectomy (removal of ovaries) increases levels, is most likely linked to the drop in the hormone estrogen, which regulates the menstrual cycle
Procedure and Patient Care
The patient should fast 10-12 hours after eating a low-fat diet before testing. Only water is permitted. Food can elevate triglyceride levels
Inform the patient that dietary intake at least 2 weeks before testing can affect results.
Tell the patient that no alcohol should be consumed 24 hours before the test.
HDL Cholesterol
Used for Cardiovascular risk assessment
HDL has the highest proportion of protein relative to lipid compared to other lipoproteins (>50% protein)
HDL cholesterol is also an important tool used to assess an individual’s risk of developing coronary heart disease since a strong negative relationship between HDL cholesterol concentration and the incidence of CHD has been reported.
Those with more physical activity have higher HDL cholesterol values.
Values >80-100 mg/dL may indicate metabolic response to certain medications or some form of chronic intoxication, such as with alcohol, heavy metals, industrial chemicals, including pesticides.
Increased risk for CHD: <40 mg/dL
Decreased risk for CHD: >60 mg/dL
Subclasses of HDL include 2a, 2b, 3a, 3b, 3c. 2b is the only subclass that is cardio protective.
People who have low Total HDL tend to have low 2b levels also.
When total HDL levels are greater than 60, levels of 2b predominate, and efficient reverse cholesterol transport takes place, and this is what protects the arteries from disease.
Smoking and alcohol ingestion decrease HDL levels
HDL values are age and sex dependent.
LDL Cholesterol
Used for evaluation of cardiovascular risk
Diagnosis of hypobetalipoproteinemia. Hypobetalipoproteinemia - constitutes a group of lipoprotein metabolism disorders that are characterized by permanently low levels (below the 5th percentile) of apolipoprotein B and LDL cholesterol.
Diagnosis of abetalipoproteinemia (values undetectable) Abetalipoproteinemia - a disorder that interferes with the normal absorption of fat and fat-soluble vitamins from food.
Decreased values may indicate hypobetalipoproteinemia
Related polyneuropathy may exist in affected individuals
LDL patterns can be identified, and they are associated with variable risks of coronary artery disease.
Pattern A is seen in patients with mostly large LDL particles and does not carry an increased risk for CAD
Pattern B is seen in patients with mostly small LDL particles and is associated with an increased risk of CAD
An intermediate pattern is noted in a large number of patients; they have small and large LDL particles and experience an intermediate risk of CAD
LDL levels can be lowered with diet, exercise, and statins
Total Cholesterol
Evaluation of cardiovascular risk
Approximately 75% of cholesterol is newly synthesized and 25% originates from dietary intake.
Moderate to markedly elevated values are also seen in cholestatic liver disease.
Values of hyperthyroidism usually are in the lower normal range; malabsorption values may be <100 mg/dL, while beta-lipoprotein B deficiency values usually are <80 mg/dL
VLDL
Are cleared in the bloodstream and the rest is converted to LDL
Carry a small amount of cholesterol, but are the predominant carriers of blood triglycerides.
Are associated with, to a lesser degree, an increased risk of CAD by virtue of their capability to be converted to LDL by lipoprotein lipase in skeletal muscle.
Triglycerides
Partly synthesized in the liver and partly derived from the diet
Very high triglyceride levels increase the risk of the development of acute pancreatitis
The degree of hypertriglyceridemia can be used to categorize patients into 4 groups.
Secondary causes of hypertriglyceridemia include: obesity, nephrotic syndrome, cushing's syndrome, estrogen replacement/oral contraceptive, HIV, paraproteinemias, diabetes mellitus, renal failure, hypothyroidism, medications, alcoholism, and autoimmune disorders.
Medications more commonly associated with high or raised triglycerides include:
Cholesterol and Triglycerides vary independently, so measurement of both is more meaningful than just measuring cholesterol only.
Triglyceride concentrations >1,000 mg/dL can lead to abdominal pain and may be life-threatening due to chylomicron-induced pancreatitis.
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