Diagnosing Lipid Disorders

NYU Langone physicians diagnose lipid disorders with blood tests and sometimes with additional imaging tests.

Lipids are waxy fats in the blood that are essential to a wide range of bodily functions. Cholesterol and triglycerides are two kinds of lipids.

Cholesterol is present in the cells of the body, and is a dietary component of non-plant foods. Triglycerides are also in the cells and in dietary fat, such as the white fat in meat, oils, and dairy products. The liver also produces cholesterol and triglycerides.

When the blood contains amounts of these substances that are outside of the healthy range—either too high or too low—this is known as a lipid disorder. People who have a high amount of certain lipids are at increased risk of developing cardiovascular disease.

Low-Density Lipoprotein

Low-density lipoprotein, known as LDL, or “bad,” cholesterol, is one of the most important components of your lipid profile. It circulates through your bloodstream and deposits cholesterol in your arteries. The cholesterol can accumulate and form plaques, which can lead to blockages that may cause a heart attack or stroke. Reducing your LDL through lifestyle changes and medications can help lower your risk.

High-Density Lipoprotein

High-density lipoprotein, or HDL—the “good” cholesterol—may help remove cholesterol from the body. A high level of HDL is associated with a reduced risk of cardiovascular disease. HDL levels are primarily influenced by genetic factors, but lifestyle changes such as tobacco cessation, weight loss, and exercise may be able to help you raise HDL levels.

Triglycerides

Triglycerides are fats that come from foods you’ve eaten and are present in your body’s cells. They are produced by the liver and fat tissue, especially when you consume excess calories, particularly from sugars and starches. The body carries triglycerides to tissues, where they provide energy or are stored, especially in fat tissue.

High levels of triglycerides have been linked to heart disease, as well as insulin resistance, type 2 diabetes, and obesity. Very high levels can also cause pancreatitis, an inflammation of the pancreas. Lifestyle changes, such as exercise, diet, and weight loss, can often help reduce triglyceride levels.

Causes and Symptoms

There are several different causes of lipid disorders. One of the most common is a genetic predisposition. Importantly, lifestyle habits can help decrease some of that risk—or worsen it.

A diet high in saturated fat, sugar, and simple carbohydrates can lead to increased lipid levels, especially triglycerides. Having increased belly fat is associated with elevated levels of LDL cholesterol, as well as high blood pressure and the risk of developing diabetes. People with diabetes, especially those who are sedentary, can also have disorders in which triglycerides accumulate in muscles or the liver, rather than being used as energy, which removes them from the body.

Taking certain medications, such as steroids, estrogen used in birth control pills, and certain medications to treat high blood pressure and psychiatric conditions, can increase lipid levels. Certain hormone disorders—including polycystic ovary syndrome (PCOS), hypothyroidism, and type 2 diabetes—can also result in high lipid levels.

A genetic disorder known as familial hypercholesterolemia, which begins in childhood, can cause chronically elevated cholesterol levels throughout a person’s lifetime. Levels may become so high that complications, such as a heart attack and stroke, can occur prematurely—even as early as the preschool years—if a person is not treated from a young age. Family members of people with the condition should be screened for it.

In the early stages of lipid disorders, there are no symptoms. High total cholesterol, high LDL, high triglycerides, and low HDL are often first detected in a routine blood test at an annual checkup. Some people with very high cholesterol and triglyceride levels may develop xanthomas—deposits of cholesterol that appear on the ankles or elbows—but this is not common.

Diagnostic Tests

To diagnose a lipid disorder, your NYU Langone doctor checks your weight, since being overweight or obese is associated with elevated lipids, cardiovascular disease, and diabetes. Then, he or she may order one or more of the following tests.

Blood Test

Your doctor orders a blood test called a lipid profile. The test, which requires you to fast the night before, measures levels of total cholesterol, LDL cholesterol, HDL cholesterol, and triglycerides—as well as other markers of health. LDL and HDL cholesterol measured on non-fasting blood are also accurate except in people with increased triglyceride levels, who may need a more specialized lipid test.

If your levels are elevated, your doctor may ask about your family history, diet, exercise habits, and other aspects of your lifestyle. He or she may perform further tests to rule out other causes of elevated lipids, such as thyroid disease, liver disease, kidney disease, and medications.

Lipid testing can give your doctor a sense of which foods you should avoid. If the results indicate that you have high levels of triglycerides, your physician is likely to recommend restricting refined carbohydrates, such as white rice and potatoes, as well as saturated and trans fats.

Advanced Lipid Testing

If your doctor wants to better understand your risk of a heart attack or stroke, and determine whether you might need intensive treatment, he or she may order advanced lipid testing.

During this test, your doctor checks your blood not just for levels of LDL and HDL, but for the number, or concentration, of these lipoproteins and their sizes. Some experts believe that this advanced assessment of lipoproteins is a more accurate predictor of cardiovascular disease then the basic lipid profile.

Coronary Calcium Score

To assess how a lipid disorder is affecting your health and whether you would benefit from treatment with medication, your doctor may order a coronary calcium score. This test involves a CT scan focused just on the area of the heart, and uses X-rays to assess the amount of calcium in your coronary arteries.

This exam enables your doctor to look for calcium deposits in the walls of your coronary arteries, which are an indication of the buildup of plaque that represents early coronary artery disease. A coronary calcium score has been shown to be an accurate reflection of a person’s risk of cardiovascular disease, and helps your doctor to determine how aggressively to treat a lipid disorder.

Carotid Intima-Media Thickness Test

A carotid intima-media thickness test is an ultrasound exam that allows the doctor to measure the amount of plaque in the neck arteries. This measurement gives your doctor an idea of how likely you are to develop cardiovascular disease.

The technician administering the test applies a thick gel to your neck, then moves a handheld device called a transducer up and down your neck. Sound waves bounce off the arteries in the neck, called the carotid arteries, and create images that are transmitted on a computer screen.

The test measures the thickness of the inner and middle layers of the arteries, the areas where cholesterol deposits first appear. An increase in the thickness of this region may be associated with higher risk of heart attack and stroke.

In addition, the amount of plaque in the neck arteries gives your doctor an idea of how much plaque may be in your coronary arteries. If a person has a large buildup of plaque, he or she may need more aggressive treatment to reduce his or her risk of heart attack and stroke.