In many patients hyperlipidemia is caused by some underlying "non-lipid" etiology rather than a primary disorder of lipid metabolism. The secondary causes of dyslipidemia will be reviewed briefly here; many of these are discussed in more detail elsewhere:
- Type 2 diabetes mellitus
- Excessive alcohol consumption
- Cholestatic liver diseases
- Nephrotic syndrome
- Chronic renal failure
- Cigarette smoking
In a cohort of 824 new patients referred to a lipid clinic at an academic medical center in the United States, 28 percent had one or more potential causes of secondary dyslipidemia . The most common conditions that were felt to be contributing to dyslipidemia were excessive alcohol intake (10 percent) and uncontrolled diabetes mellitus (8 percent).
TYPE 2 DIABETES MELLITUS
Hyperlipidemia in association with insulin resistance is common in patients with type 2 diabetes mellitus (DM) [2,3]. Insulin resistance and the ensuing hyperinsulinemia are associated with hypertriglyceridemia and low serum high-density lipoprotein (HDL) cholesterol concentrations.
The lipoprotein abnormalities are related to the severity of the insulin resistance. A study that measured insulin sensitivity using a euglycemic clamp in patients with and without type 2 DM found that greater insulin resistance was associated with larger very low density lipoprotein (VLDL) particle size, smaller low density lipoprotein (LDL) particle size, and smaller HDL particle size . Additionally, the number of VLDL, intermediate density lipoprotein (IDL), and LDL particles increase with increasing insulin resistance, while HDL particle concentration decreases.