Merck Manual

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    Cholesterol is a type of lipid—an essential element contained in all human cells. However, excess lipids and other fatty substances in the blood can cause hyperlipidemia and other lipid disorders. Hyperlipidemia is a significant risk factor for development of atherosclerosis and heart disease.

    The cardiovascular system comprises the heart, blood vessels, and blood. Blood has many life-sustaining responsibilities, including transporting oxygen, carbon dioxide, nutrients, and hormones throughout the body. Blood contains red blood cells, white blood cells, platelets, and nutrients. Cholesterol also circulates in the blood stream.

    Two common forms of cholesterol are LDL, known as the "bad cholesterol" and HDL, known as the "good cholesterol." Hyperlipidemia is the term used when the blood contains a higher amount of LDL than is recommended.

    Cholesterol and other fatty substances combine in the bloodstream and are deposited in the blood vessels to form a material called plaque. The increase in lipids can cause plaques to grow over time, leading to obstructions in blood flow. If an obstruction occurs in the coronary arteries, it could result in a heart attack. And, if an obstruction occurs in the arteries of the brain, it could lead to stroke.

    Causes of hyperlipidemia can include heredity and taking certain medications. However, the greatest, modifiable risk factor is diet; a poor diet is one with a fat intake greater than 40% of total calories, saturated fat intake greater than 10% of total calories; and cholesterol intake greater than 300 milligrams per day.

    There are no symptoms of hyperlipidemia, so regular cholesterol screening with blood tests should be part of the physical examination. A doctor or healthcare professional can recommend ways to prevent hyperlipidemia.