LDL and HDL Cholesterol: What's Bad and What's Good?

 

 

 

 

 

 

 

 

LDL and HDL Cholesterol: What's Bad and What's Good?

 

Cholesterol can’t dissolve in the blood. It has to be transported to and from the cells by carriers called lipoproteins. Low-density lipoprotein, or LDL, is known as “bad” cholesterol. High-density lipoprotein, or HDL, is known as “good” cholesterol. These two types of lipids, along with triglycerides and Lp(a) cholesterol, make up your total cholesterol count, which can be determined through a blood test. 

 

 

LDL (Bad) Cholesterol
When too much LDL (bad) cholesterol circulates in the blood, it can slowly build up in the inner walls of the arteries that feed the heart and brain. Together with other substances, it can form plaque, a thick, hard deposit that can narrow the arteries and make them less flexible. This condition is known as atherosclerosis. If a clot forms and blocks a narrowed artery, heart attack or stroke can result.

 

 

HDL (good) Cholesterol
About one-fourth to one-third of blood cholesterol is carried by high-density lipoprotein (HDL). HDL cholesterol is known as “good” cholesterol, because high levels of HDL seem to protect against heart attack. Low levels of HDL (less than 40 mg/dL) also increase the risk of heart disease. Medical experts think that HDL tends to carry cholesterol away from the arteries and back to the liver, where it's passed from the body. Some experts believe that HDL removes excess cholesterol from arterial plaque, slowing its buildup.

 

 

Triglycerides
Triglyceride is a form of fat made in the body. Elevated triglycerides can be due to overweight/obesity, physical inactivity, cigarette smoking, excess alcohol consumption and a diet very high in carbohydrates (60 percent of total calories or more). People with high triglycerides often have a high total cholesterol level, including a high LDL (bad) level and a low HDL (good) level. Many people with heart disease and/or diabetes also have high triglyceride levels.

 

 

Lp(a) Cholesterol
Lp(a) is a genetic variation of LDL (bad) cholesterol. A high level of Lp(a) is a significant risk factor for the premature development of fatty deposits in arteries. Lp(a) isn’t fully understood, but it may interact with substances found in artery walls and contribute to the buildup of fatty deposits.

 

 

 

 

 

Atherosclerosis

 

 

Atherosclerosis is a type of arteriosclerosis. The name comes from the Greek words athero (meaning gruel or paste) and sclerosis (hardness). It's the term for the process of fatty substances, cholesterol, cellular waste products, calcium and fibrin (a clotting material in the blood) building up in the inner lining of an artery. The buildup that results is called plaque.

 

Arteriosclerosis is a general term for the thickening and hardening of arteries. Some hardening of arteries normally occurs when people grow older.

Plaque may partially or totally block the blood's flow through an artery.

 

Two things that can happen where plaque occurs are:

• There may be bleeding (hemorrhage) into the plaque.
• A blood clot (thrombus) may form on the plaque's surface.

If either of these occurs and blocks the whole artery, a heart attack or stroke may result.

Atherosclerosis affects large and medium-sized arteries. The type of artery and where the plaque develops varies with each person.

Atherosclerosis is a slow, progressive disease that may start in childhood. In some people this disease progresses rapidly in their third decade. In others it doesn't become threatening until they're in their 50s or 60s.

 

 

How does atherosclerosis start?

It's a complex process. Exactly how atherosclerosis begins or what causes it isn't known, but some theories have been proposed. Many scientists think atherosclerosis starts because the innermost layer of the artery becomes damaged. This layer is called the endothelium. Three possible causes of damage to the arterial wall are:

• Elevated levels of cholesterol and triglyceride in the blood
• High blood pressure
• Cigarette smoke

Cigarette smoke greatly aggravates and speeds up the growth of atherosclerosis in the coronary arteries, the aorta and the arteries of the legs.

 

Because of the damage, over time fats, cholesterol, platelets, cellular debris and calcium are deposited in the artery wall. These substances may stimulate the cells of the artery wall to produce still other substances. This results in more cells accumulating in the innermost layer of the artery wall where the atherosclerotic lesions form. These cells accumulate, and many of them divide. At the same time, fat builds up within and around these cells. They also form connective tissue.

 

The innermost layer of the artery becomes markedly thickened by these accumulating cells and surrounding material. If the wall is thickened sufficiently, the diameter of the artery will be reduced and less blood will flow, thus decreasing the oxygen supply.

Often a blood clot forms and blocks the artery, stopping the flow of blood. If the oxygen supply to the heart muscle is reduced, a heart attack can occur. If the oxygen supply to the brain is cut off, a stroke can occur. And if the oxygen supply to the extremities occurs, gangrene can result.

 

 

 

 

Atherosclerosis is a disease affecting blood vessels called arteries. Fatty material called plaque builds up within the inner lining of arteries causing them to narrow and be less flexible. This reduces the amount of blood and oxygen that is delivered to vital organs. Atherosclerosis can occur anywhere in your body, but it is especially dangerous when it affects the arteries leading to your brain, heart, kidneys and legs.

 

Complications of atherosclerosis include: stroke or TIA in the brain, angina (chest pain), heart attack, sudden death, heart failure kidney failure, erectile dysfunction and PAD (peripheral artery disease).

 

 

 

 

 

 

http://www.americanheart.org/presenter.jhtml?identifier=180