Hyperlipidemia is a term used to describe increased levels of lipids in blood, be that in the form of cholesterol (HDL, LDL, IDL or VLDL) or triglycerides. Though not a disease itself, hyperlipidemia has the potential to predispose to several diseases.
The most common presentation of hyperlipidemia is a cardiovascular event. Patients are typically overweight, lethargic and may have one or multiple xanthomas on their skin. They may also be suffering from other diseases like diabetes or pancreatitis. In case of homozygous familial types, presentation is often similar to that of ischemic heart disease. In heterozygous types, the patients are often asymptomatic.
There may also be tendon xanthomas, xanthelasmas (yellow coloured lesions on eyelids) and corneal arcus (gray coloured opacity on periphery of cornea). The most commonly found ophthalmologic abnormalities occurring in patients with hyperlipidemia include corneal arcus, lipemia retinalis, and xanthelasma . Patients may also complain of abdominal pain, nausea, vomiting and sometimes dyspnea.
All potential underlying diseases should be tested and methodically excluded with the help of history and laboratory tests. The elevated lipids should be checked with the help of a lipid analysis and imaging studies should be conducted to reveal the extent of damage to the vasculature and other organs.
Primary medication used to effectively treat the condition is statins. Statins are a class of drugs that lower circulating cholesterol levels by inhibiting HMG-CoA reductase , which is the rate-limiting enzyme in hepatic cholesterol biosynthesis . Other drugs include fibrates, to control high triglyceride levels, bile resins and sequestrants for hypercholesterolemia, and niacin. Lipid apheresis may also be used to treat patients with severe hyperlipidemia by reducing low-density lipoprotein cholesterol (LDL-C) levels . The parallel mode of treatment includes lifestyle modifications and a carefully controlled diet.
Prognosis depends heavily on management. If the hyperlipidemia, be it familial or secondary, is appropriately managed with drugs, appropriate diet and lifestyle modifications, the prognosis is fairly positive. However, if the condition is not managed, there is a negative prognosis and a high rate of mortality. Epidemiologic studies found a direct relationship between the total cholesterol levels and risk of coronary disease . Indeed the high mortality can be attributed to cardiovascular diseases.
Hyperlipidemia may be primary , for example familial hyperlipidemia (FH), or secondary meaning it occurs as a consequence of other diseases that disturb lipid metabolism , for example diabetes mellitus. Hyperlipidemia in association with insulin resistance is a common occurrence in patients suffering from diabetes mellitus type II (DM 2) .
In case of FH, the causative factors are inherited mutations in genes like APOB, APOC2 etc, deficiency of the lipoprotein lipase enzyme (LPL) or disturbed functioning of LDL receptors. Acquired hyperlipidemias are caused by diseases that interfere with lipid metabolism and uptake into cells.
CDC conducted a survey of the prevalence of hyperlipidemia with respect to body mass index (BMI) between 1999 and 2006 and it reported a prevalence of 14.2% in normal weight individuals, 22.3% in overweight individuals and 42.9% in the obese .
Hyperlipidemia may present in the youth in familial cases but non-familial cases usually present much later in life.
Hyperlipidemia tends to be slightly more common in men than women.
Primary hyperlipidemias can be classified on the basis of the type of elevated lipoproteins found in the blood, using the Fredrickson criteria :
Secondary hyperlipidemias or acquired hyperlipidemias are a consequence of underlying disease such as hypothyroidism, renal failure, excessive intake of alcohol, diabetes, metabolic syndrome or chronic pancreatitis. The elevated lipids are either a consequence of direct damage to the liver, and thus the lipid metabolism, or due to nonenzymatic glycosylation of blood vessel as in diabetes, pancreatitis due to alcoholism or high absorption from the gut due to increased intake as in obese individuals.
Hyperlipidemia can easily be prevented by exhibiting a healthy lifestyle. Good cholesterol (HDL) should be kept elevated and bad cholesterol (LDL) should be kept in reduced limits. Exercise and moderate consumption of ethanol raise HDL levels, whereas obesity and smoking lower it . So a healthy lifestyle demonstrated by regular exercise, controlled diet and avoiding smoking and excessive alcohol can go a long way in both preventing the occurrence of, as well as the progress of hyperlipidemia.
Hyperlipidemia is a disorder of increased lipid or lipoprotein levels and is the most common form of dyslipidemia. Lipids are a group of biological organic compounds that are insoluble in water but soluble in organic solvents. For the purpose of adhering strictly to the human body and the phenomenon of hyperlipidemia, lipids are classified into 6 types. They are: High density lipids (HDL), low density lipids (LDL), Intermediate density lipids (IDL), very low density lipids (VLDL), triglycerides and cholesterol. If any one or more of these types become abnormally elevated in the blood, it is known as hyperlipidemia.
It can be genetic, known as primary or familial hyperlipidemia due to inherited mutations or it can be acquired; as a consequence of an extravagant lifestyle or underlying disease.
Signs and symptoms
It may be asymptomatic initially and typically presents late in the form of a cardiovascular event. Infants may present with signs similar to ischemic heart disease and small raised yellow coloured lesions on the skin (xanthomas). Adults may also have xanthomas either on the skin or in their tendons.
Diagnosis is based on excluding or identifying underlying disease, and measuring lipid levels in the blood. A detailed history also helps in diagnosing familial types.
Treatment includes dietery and lifestyle modifications and drugs.