Lipids are non-water soluble, hydrophobic group of molecules that occur naturally in the body. Lipids serve many important functions. They are the building blocks of the human cell membranes, serve as messenger hormones and are an important source of energy. Some categories of lipids in the human body includes fatty acids, cholesterols, and triglycerides.
A lipid disorder refers to a range of conditions that cause abnormal levels of lipids in the blood. The commonest lipid disorders seen in clinical practice are hypercholesterolemia (high blood cholesterol) and hypertriglyceridemia (high blood triglycerides).
Cholesterol is a class of lipids found in humans and other animals. It is primarily produced by the liver but can also be obtained through the consumption of animal products. Its primary role is in the building or human cell membranes and nerve membranes.
Cholesterol, being an insoluble fatty substance, is transported in the bloodstream by carrier proteins known as lipoproteins. There are many transporter lipoproteins in the body, but the two most commonly measured lipoproteins are high-density lipoprotein (HDL) and low-density lipoprotein (LDL).
HDL is known as the 'good cholesterol' as it is involved in the removal of cholesterol from the body tissues, delivering the cholesterol to the liver to be metabolised and eventually excreted from the body. On the other hand, LDL is known as the 'bad cholesterol' as it is involved in delivering cholesterol to body tissues which can cause unhealthy cholesterol build-up, most significantly in the blood vessels.
Triglycerides are blood fats produced by the liver, as well as derived from the food we eat. Triglycerides are used by the body as a source of energy. Excess triglycerides are stored in fat cells around the body, for use later. This contributes to obesity.
| Desirable lipid levels in adults (aged >18 years) | |
|---|---|
| Total cholesterol (mmol/ dL) | <5.2 |
| Triglycerides (mmol/ dL) | <2.3 |
| High density lipoprotein, HDL (mmol/ dL) | >1.0 |
| Low density lipoprotein, LDL (mmol/ dL) | <3.4 |
Desired lipid levels (specifically LDL) will also vary according to a patient's background cardiovascular risk profile. This will be discussed individually to patients, by the attending cardiologist.
Elevated blood lipids refer to elevated LDL levels and/ or elevated triglyceride levels. Common causes include:
Elevated blood lipids do not cause symptoms in early stages. In cases of chronic high blood cholesterol, some patients develop fatty deposits around their eyes (xanthelasma) or fatty nodules along tendons of the hands and ankles (tendon xanthoma).
High blood cholesterol is a major cause of cardiovascular and cerebrovascular diseases. High LDL levels can promote delivery of cholesterol to various body organs, including the blood vessels. Cholesterol build-up in blood vessels can potentially cause obstruction of blood flow to various important body organ systems, such as the heart, the brain, or the kidneys. It is a major cause of heart attacks and strokes worldwide.
High triglyceride levels are also known to cause pancreatitis (inflammation of the pancreas).
Once diagnosed with a lipid disorder, the patient will be managed in a multi-disciplinary manner. Lifestyle interventions will be recommended. These interventions include introduction of healthy eating habits, increasing exercise, weight loss, smoking cessation, and reduction in alcohol intake. Should the lipid levels be still not optimal with lifestyle changes, medications can be initiated to effectively reduce cholesterol or triglyceride levels.
The optimal treatment regime for lipid disorders will need to be carefully tailored to each patient's unique individual characteristics.
