Total Cholesterol (TC) Test: Meaning, Production, Functions, High & Low Levels, Causes, Symptoms, and Complete Guide
Introduction
Cholesterol is a natural fatty substance (lipid) that is essential for several body functions. Although it is commonly associated with heart disease and blocked arteries, cholesterol itself is not harmful. In fact, the body needs cholesterol to build cells, produce hormones, and create vitamin D. Problems arise only when cholesterol levels become too high or too low, disrupting normal physiological balance.
The Total Cholesterol (TC) Test measures the complete amount of cholesterol circulating in the blood. This includes LDL (bad), HDL (good), VLDL, and other lipoproteins. Because cholesterol is linked closely to heart health, the TC test is one of the most important screening tests for evaluating cardiovascular risk. It is usually included in a Lipid Profile Panel.
This detailed guide explains everything about the Total Cholesterol Test in simple language, helping patients, students, and professionals understand the test completely.
What Is Total Cholesterol (TC)?
Total Cholesterol represents the sum of all cholesterol particles in the bloodstream. Cholesterol cannot travel alone in the blood, so it binds to proteins, forming lipoprotein particles. These include:
- LDL (Low-Density Lipoprotein) – Known as “bad cholesterol” because excess LDL forms plaque inside arteries.
- HDL (High-Density Lipoprotein) – Called “good cholesterol” because it removes extra cholesterol from blood vessels.
- VLDL (Very-Low-Density Lipoprotein) – A particle that mainly carries triglycerides.
- Intermediate-density lipoproteins and remnants.
The TC test gives a broad overview of cholesterol health, helping doctors understand whether a person is at risk for blocked arteries, stroke, or coronary artery disease.
Where Is Cholesterol Produced in the Body?
Cholesterol enters the body from two sources: internal production and dietary intake.
1. Internal Production (Endogenous) – 80%
The majority of cholesterol is produced inside the body, mainly by the:
- Liver
- Intestines
- Adrenal glands
- Reproductive organs (ovaries/testes)
The liver plays the biggest role by tightly regulating cholesterol production. Even when you eat more cholesterol, the liver reduces internal production to maintain balance.
2. Dietary Intake – 20%
Cholesterol is also absorbed from foods such as:
- Eggs
- Chicken
- Meat
- Dairy products
- Fried foods
- Fast food and bakery items
While diet affects cholesterol levels, genetics, liver function, hormones, and lifestyle have a much stronger influence.
Functions and Importance of Cholesterol
Cholesterol is crucial for several basic body functions. Without it, survival would be impossible.
1. Builds Cell Membranes
Cholesterol stabilizes and strengthens the membrane of every cell in the body.
2. Helps in Hormone Production
Important hormones are made using cholesterol, including:
- Estrogen
- Testosterone
- Cortisol
- Progesterone
These hormones regulate mood, fertility, metabolism, and stress response.
3. Produces Vitamin D
Sunlight converts cholesterol into vitamin D, essential for:
- Strong bones
- Immunity
- Calcium absorption
4. Formation of Bile Acids
Cholesterol forms bile acids, which help digest fats and absorb vitamins A, D, E, and K.
Even though cholesterol is vital, maintaining the right balance is key to preventing heart and metabolic diseases.
Causes of Low Total Cholesterol (Hypocholesterolemia)
Low cholesterol is less common and may indicate underlying health issues. Common causes include:
1. Malnutrition or Poor Diet
Low intake of proteins, fats, and calories reduces cholesterol levels.
2. Hyperthyroidism
An overactive thyroid speeds up metabolism, lowering cholesterol.
3. Chronic Liver Disease
Damaged liver cells produce less cholesterol.
4. Cancers
Certain cancers increase cholesterol breakdown.
5. Chronic Infections
Long-standing infections such as tuberculosis can reduce cholesterol.
6. Genetic Disorders
Inherited lipid abnormalities may cause extremely low cholesterol.
7. Excessive Use of Statins
Cholesterol-lowering drugs sometimes reduce cholesterol too much.
Symptoms of Low Cholesterol
Low cholesterol usually has subtle or no symptoms, but severe deficiency may cause:
- Hormonal imbalance
- Fatigue
- Low mood or depression
- Anxiety or irritability
- Poor stress handling
- Weak immunity
Very low cholesterol affects the nervous system and mental well-being because brain cells need cholesterol to function normally.
Causes of High Total Cholesterol (Hypercholesterolemia)
High cholesterol is much more common and is strongly linked to heart disease.
1. Unhealthy Diet
Excess intake of:
- Fried foods
- Red meat
- Butter and ghee
- Cheese
- Fast food
increases LDL and total cholesterol.
2. Obesity and Lack of Exercise
Sedentary lifestyle slows down fat metabolism.
3. Genetic Disorders
Familial hypercholesterolemia causes extremely high cholesterol even in young age.
4. Hypothyroidism
Low thyroid hormone raises LDL levels.
5. Diabetes and Insulin Resistance
High insulin levels cause abnormal lipid metabolism.
6. Liver or Kidney Disorders
These conditions interfere with cholesterol breakdown.
7. Smoking and Alcohol
Smoking lowers HDL, while alcohol raises triglycerides and VLDL.
8. Certain Medications
Examples:
- Steroids
- Diuretics
- Oral contraceptives
- Immunosuppressants
Symptoms of High Cholesterol
High cholesterol is known as a “silent risk factor” because it develops slowly without symptoms. However, long-term elevation may cause:
- Chest pain (angina)
- Risk of heart attack
- Risk of stroke
- Xanthomas (fatty skin deposits)
- Xanthelasma (yellow patches near eyes)
- Numbness or poor circulation
Because symptoms appear late, regular testing is important.
Reference Ranges for Total Cholesterol
- Less than 200 mg/dL – Desirable
- 200–239 mg/dL – Borderline High
- 240 mg/dL or above – High
(200 mg/dL ≈ 5.2 mmol/L)
Doctors interpret TC values along with LDL, HDL, and triglycerides for accurate risk assessment.
Sample Type and Collection
- Sample Type: Serum
- Tube Used: Red-top (plain tube)
A simple venous blood sample is taken, usually as part of a full lipid profile.
Test Preparation
For accurate results:
- Fast for 8–12 hours (water allowed)
- Avoid alcohol for 24–48 hours
- Inform doctor about statins, steroids, or diuretics
- Eat normally in the days before the test (no sudden diet changes)
When to Consult a Doctor
You should see your doctor if you:
- Have high or borderline cholesterol levels
- Experience chest pain or shortness of breath
- Notice yellow cholesterol deposits on skin
- Have family history of heart disease
- Have diabetes, hypertension, or obesity
- Smoke or consume alcohol regularly
Early detection and management can significantly reduce long-term heart risks.
Important Word Explanations
- LDL: “Bad cholesterol” that builds plaque in arteries.
- HDL: “Good cholesterol” that removes excess cholesterol.
- VLDL: Lipoprotein carrying triglycerides; contributes to plaque.
- Atherosclerosis: Hardening and narrowing of arteries due to plaque buildup.
- Xanthomas: Fatty skin growths caused by very high cholesterol.
- Xanthelasma: Yellowish deposits around the eyes due to cholesterol.
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