Dyslipidemia (high blood fats)

What is dyslipidemia?

Dyslipidemia is the presence of an abnormally high level of lipids (fats) or lipoproteins (fat-carrying proteins) in the blood. Lipids are an important part of the body - they are crucial in the formation of cells and as an energy source that our body can break down and use. Sometimes the level of lipids can be abnormally high, which can cause health risks. High levels of lipids and lipoproteins in the blood can build up in the arteries, causing them to harden, become narrow and restrict blood flow, leading to heart attack or stroke.

What are lipids?

Lipids, commonly known as fats, consist of cholesterol and triglycerides. Cholesterol is an essential component of all cells. Triglycerides are an important energy source for the body.

Cholesterol and triglycerides need to be bound to proteins, known as lipoproteins, for them to be transported in the bloodstream to all areas of the body. There are many different lipoproteins with different functions, which collectively help control the level of triglyercides and cholesterol in the blood. The two main lipoproteins that have the greatest influence on the level of cholesterol and triglycerides in the blood are low-density lipoproteins (LDL) and high-density lipoproteins (HDL). LDL help move lipids from the liver to around the body, and often into blood vessel walls. The progressive accumulation of lipids in the vessel walls gives rise to the abnormal hardening and narrowing of blood vessels, known as atherosclerosis. For this reason, LDL is known as 'bad fats'. In contrast, HDL help move lipids to the liver for disposal, hence helping to reduce the risk of artherosclerosis. HDL are known as 'good fats'.

An excess of cholesterol and triglycerides can pose a risk to a person's health. Numerous factors can lead to high blood lipids, including intake of excess dietary fats, imbalance in lipoprotein levels, cigarette smoking, or certain medications.

Causes

The causes of dyslipidemia are classed as either primary (genetic), or secondary (lifestyle and other causes).

Primary causes

Primary causes refer to gene mutations that alter the production of lipids or lipoproteins. Genes are comprised of DNA and are the codes within your cells that define what gets made - similar to a recipe. Sometimes, genes can mutate to create more or less of what they are supposed to make. Some people with dyslipidemia have genes that create excess triglycerides, cholesterol or LDL. Alternatively, they could have genes that cause the underproduction of HDL. Individuals with gene mutations tend to have a family history of the condition.

Secondary causes

Secondary causes of dyslipidemia are related to lifestyle or other medical conditions. A common cause of dyslipidemia is a diet rich in oily or processed foods; in particular, a diet that contains too much saturated fat, cholesterol and trans fats, but is low in unsaturated fats (these are considered healthy fats, which can lower blood cholesterol levels and the risk of heart disease).

Other causes can include:

• Hypothyroidism;
• Kidney failure;
• Diabetes (particularly type 2 diabetes);
• Liver diseases;
• Obesity, and;
• Medications including thiazides, beta-blockers, retinoids, antiretroviral agents, cyclosporine, estrogen, progestins and glucocorticoids.

Types

Dyslipidemia can be classified into various types, depending on which lipid there is too much of in the blood. The types include:

• Hypertriglyceridemia (excess triglycerides in the blood);
• Hypercholesterolemia (excess cholesterol in the blood);
• Mixed pattern dyslipidemia, which is a combination of the above types.

Signs and symptoms

In most cases, dyslipidemia does not have any symptoms. It is therefore important to monitor the levels of the different types of lipids in your blood via blood tests. In some cases, dyslipidemia can lead to more serious conditions that do have symptoms, such as heart disease and pancreatitis. Rarely, dyslipidemia can lead to fatty deposits in the iris of the eye (which appears as a white ring around the iris), within tendons (which appear as painless nodules around joints, called xanthoma) and under the skin (which appear as yellow lesions on and around the eyes, called xanthelasma).

Methods for diagnosis

Dyslipidemia is diagnosed using a blood test. This identifies the levels of various lipids including triglycerides, total cholesterol, cholesterol bound to LDL (LDL cholesterol) and cholesterol bound to HDL (HDL cholesterol). To get the most accurate result, this is done as a 'fasting test', in which you do not eat for a period of time before your test.

Other tests that your doctor may perform include measuring your levels of glucose, liver enzymes, creatinine, thyroid-stimulating hormone and urinary protein.

Types of treatment

The aim of treatment is to alter the amount of lipids in your blood to a healthy level. The general recommended goals include reducing triglyceride levels to less than 150 mg/dL, total cholesterol to less than 200 mg/dL and LDL cholesterol to less than 100 mg/dL, and increasing HDL cholesterol to more than 40 mg/dL. However, if you have certain underlying medical conditions, such as diabetes, some of these target levels are even lower.

If your lipid levels are only slightly outside the healthy range, diet and lifestyle changes may be the only treatment required. If your condition is more severe, your doctor can prescribe medications to alter your cholesterol and triglyceride levels.

Cholesterol levels are measured in milligrams (mg) of cholesterol per deciliter (dL) of blood. You can use these general guidelines to interpret your test results.

Total cholesterol

• Below 200 mg/dL - Desirable
• 200-239 mg/dL - Borderline high
• 240 mg/dL and above - High

LDL cholesterol

• Below 70 mg/dL - Best for people who have heart disease or diabetes.
• Below 100 mg/dL - Optimal for people at risk of heart disease.
• 100-129 mg/dL - Near optimal if there is no heart disease. High if there is heart disease.
• 130-159 mg/dL - Borderline high if there is no heart disease. High if there is heart disease.
• 160-189 mg/dL - High if there is no heart disease. Very high if there is heart disease.
• 190 mg/dL and above - Very high.

HDL cholesterol

• Below 40 mg/dL - Poor
• 40-59 mg/dL - Better
• 60 mg/dL and above - Best

Triglycerides

• Below 150 mg/dL - Desirable
• 150-199 mg/dL - Borderline high
• 200-499 mg/dL - High
• 500 mg/dL and above - Very high

If your results show that your cholesterol level is high, don't get discouraged. You may be able to lower your cholesterol with lifestyle changes, such as quitting smoking, exercising and eating a healthy diet. If lifestyle changes aren't enough, cholesterol-lowering medications also may help. Talk to your doctor about the best way for you to lower your cholesterol.

Diet and lifestyle changes

Diet and lifestyle changes that can help to treat dyslipidemia include:

• Keeping a healthy body weight;
• Healthy eating by reducing your intake of foods that have a high fat, cholesterol and salt content;
• Eating more fiber, fruit and green vegetables and fish;
• Reducing your alcohol intake;
• Quitting smoking;
• Exercising regularly, and;
• Drinking more water.

Medications

Depending on the type of lipid disorder, various lipid-lowering medications can be used. Your doctor may prescribe one or more of the following medications:

• Statins including atorvastatin, pravastatin, simvastatin, fluvastatin and rosuvastatin;
• Bile acid-binding resins including cholestyramine and colestipol;
• Fibrates including gemfibrozil and fenofibrate, and;
• Other agents including ezetimibe, nicotinic acid, probucol and fish oils.

Potential complications

Potential complications associated with dyslipidemia are related to excess lipids building up in the inner walls of your arteries over time - this is known as atherosclerosis, which causes the arteries to harden and narrow. When this occurs in the arteries that supply blood to the heart, it can cause a condition called coronary artery disease. If an artery becomes completely blocked by a blood clot, it can stop the flow of blood to the heart, preventing the heart tissue from getting enough oxygen. This can cause a heart attack. Coronary artery disease can also cause the heart to weaken over time and contribute to congestive heart failure. Dyslipidemia can also cause peripheral vascular disease, which involves atherosclerosis occurring in other parts of your body. In addition, it can also lead to a stroke.

Prognosis

In most cases, dyslipidemia is a treatable condition. For some people, this involves making diet and lifestyle changes, while for others it will also require them to take medication to bring lipid levels into a healthy range. It is important to begin treatment as soon as possible to avoid any long-term complications associated with dyslipidemia.

Prevention

In some cases, dyslipidemia can be caused by gene mutations creating high levels of lipids in the blood. Gene mutations cannot be prevented. In many other cases, however, dyslipidemia is caused by diet and lifestyle factors that can be altered to help prevent the condition. These can include maintaining a healthy body weight, reducing fat, avoiding food high in fat and salt, eating more fruit and vegetables and fish, quitting smoking and exercising regularly. It is important to have regular blood tests as part of your general health checks, particularly if you are overweight or have a history of dyslipidemia. This can help to identify any abnormal levels of lipids in your blood and make a treatment plan.

References

1. Murtagh John MD. John Murtagh's General Practice. 5th Revised edition edition. North Ryde N.S.W. McGraw-Hill Medical Publishing 2011.
2. Cholesterol. Better Health Channel. Accessed August 8 2014. link here
3. Dyslipidemia: Lipid Disorders: Merck Manual Professional. Accessed August 8 2014. link here
4. Murtagh John MD. John Murtaghs General Practice. 5th Revised edition edition. North Ryde N.S.W.: McGraw-Hill Medical Publishing 2011.
5. Secondary Causes of Dyslipidemia. Accessed August 8 2014. link here
6. Treatment of Dyslipidemia in the Older Adult. Accessed August 8 2014. link here

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