Dyslipidemia is a condition characterized by either an increase or decrease in concentration of lipids in the blood. Hyperlipidemia, which refers to an increase in cholesterol, triglyceride (TG), or both, is the most common form of dyslipidemia. Hyperlipidemias can be classified as familial (also called primary) caused by an inherited gene mutation, or acquired (also called secondary) when resulting from underlying disorders that lead to alterations in plasma lipid and lipoprotein metabolism. The causes of acquired hyperlipidemia include dietary, alcohol intake, oral contraceptives, diabetes mellitus, and pharmacological agents (e.g., retinoic acid derivatives, steroids, and beta-blockers). Familial hyperlipidemias are classified according to the Fredrickson classification (hyperlipoproteinemia types I to V) which is based on lipoprotein analyses by electrophoresis or ultracentrifugation. It was later adopted by the World Health Organization (WHO). Hyperlipidemias are also classified according to which types of lipids are elevated. Hypercholesterolemia, hypertriglyceridemia, and combined hyperlipidemia refer to elevations involving the major cholesterol-rich lipoproteins (LDL), triglyceride-rich lipoproteins (VLDL), and both, respectively.
