Hypercholesterolemia and Hypocholesterolemia

Cholesterol and atherosclerosis

High blood cholesterol, especially LDL and triglycerides when combined with a low level of HDL can lead to atherosclerosis. Atherosclerosis mainly causes deposition of cholesterol in the walls of the arteries. This leads to build up of plaques inside the arteries of the heart and other parts of the body. Plaque is made up of cholesterol, fat, calcium, and other substances found in the blood.

Plaque also leads to hardening and narrowing of the blood vessels. This limits the flow of oxygen-rich blood to the heart and other vital organs. This can lead to heart diseases like angina and heart attack (if the coronary heart vessels are affected) and stroke (if those in brain are affected). This is a leading cause of death in the United States and worldwide.

Detection of hypercholestrolemia

High cholesterol itself does not have symptoms. Most people do not know that their cholesterol level is high unless a chance blood test reveals it. In some a heart attack or a stroke may be the first indicator of atherosclerosis and hyperlipidemia.

Blood cholesterol is detected using blood tests. Adults over the age of 20 should get their cholesterol levels checked every five years. The blood test is done after a 9- to 12-hour fast. Usually the total cholesterol is checked first. If the levels are 200 mg/dL or more, or if HDL cholesterol is less than 40 mg/dL, a detailed lipoprotein profile is required.

In the United Kingdom, the numbers are decided upon by the National Institute for Health and Clinical Excellence (NICE) and Department of Health cholesterol guidelines. They state that normal levels of total cholesterol should be less than 5.0mmol/l and for LDL it should be less than 3.0mmol/l. Joint British Societies however lay down more stringent levels at total cholesterol less than 4.0mmol/l and LDL below 2.0mmol/l.

How to compare the numbers?

To convert mg/dl to mmol/L (used in Europe, Canada and other parts of the world) the number in mg/dl is to be divided by 40.

Risk factors for hypercholesterolemia

About one in every six adult Americans has high cholesterol according to the Centre for Disease Prevention and Control (CDC). Some of the major risk factors that predispose a person to develop high blood cholesterol include:

  • Age – advancing age normally leads to hardening of arteries and disturbed cholesterol metabolism regulation
  • Sex – men are more at risk of developing high blood cholesterol of hypelipidemia/hypercholestrolemia.
  • Heredity – genes determine the predisposition to hyperlipidemia - this is especially true in cases of affected children and young adults - this is called familial hyperchiolestrolemia
  • Unhealthy dietary habits – a diet rich in saturated fats increases the risk of high blood cholesterol
  • Obesity and being overweight – this is a direct risk factor for hyperlipidemia
  • Not getting enough exercise
  • Those with Diabetes

Familial hypercholesterolemia

Familial hypercholesterolemia occurs when high blood cholesterol is inherited. Patients usually have sustained high levels of LDL cholesterol. The increased LDL levels eventually lead to early onset of heart and artery disease.

FH is also known as Type IIA hyperlipoproteinemia or Hypercholesterolemic xanthomatosis. There is a mutation in the LDL receptor gene on chromosome 19.  This mutation leads to an inability of the liver cells to make the LDL receptors. These receptors normally bind and transport LDL to the inside of the cell.  Once inside, LDL is broken down to release the cholesterol for use. Lack of this receptor means high levels of LDL in blood.

FH in its heterozygous form occurs in around 1 in 500 people in Europe and North America.  The occurrence of FH has an increased risk in South African Afrikaners, Jewish populations, and Indians.

Symptoms of FH include very early onset of cardiovascular disease like coronary artery disease. Cholesterol builds up in tendons and skin and are called tendinous xanthomas or a xanthoma. A Xanthoma has a waxy yellow appearance.  Cholesterol deposits in the eyelids are called xanthelasmas.

FH is detected through a combination of clinical testing and taking family history and analyzing for signs of early cholesterol and heart problems.

How is high blood cholesterol treated?

Lowering high cholesterol levels is important for people at all ages. This helps in preventing heart disease. The primary measures include maintaining a healthy body weight, adopting a good and healthy diet, increasing physical activities, quitting smoking, reducing alcohol use  and finally use of cholesterol lowering medications. Major cholesterol lowering medications include Statins. Others include Niacin, Fibrates etc.


Some people might also develop low blood cholesterol. There is little research on the dangers of low blood cholesterol. Some studies indicate that a low blood cholesterol may be linked to depression, bleeding within the brain (cerebral haemorrhage) and some cancers. Low blood cholesterol may usually be a result of a disease rather than a disease in itself.

Further Reading

Last Updated: Jun 20, 2023

Dr. Ananya Mandal

Written by

Dr. Ananya Mandal

Dr. Ananya Mandal is a doctor by profession, lecturer by vocation and a medical writer by passion. She specialized in Clinical Pharmacology after her bachelor's (MBBS). For her, health communication is not just writing complicated reviews for professionals but making medical knowledge understandable and available to the general public as well.


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