(2) Very low-density Lipoprotein (VLDL): Still carries a large lipid (TG)
content but includes about 10% to 15% cholesterol; formed in the liver from
endogenous fat sources.
(3) Intermediate-density Lipoprotein (IDL): Continues the delivery of
endogenous TG to cells and carries about 30% cholesterol.
(4) Low-density Lipoprotein (LDL): Carries in addition to other lipids about
two thirds or more of the total plasma cholesterol; formed in the serum from catabolism
of VLDL. Because LDL carries cholesterol to the cells for deposit in the tissues, it is
considered the main agent of concern in elevated serum cholesterol levels.
(5) High-density Lipoprotein (HDL): Carries less total lipid and more protein;
it is also formed in the liver from endogenous fat sources. Because HDL carries
cholesterol from the tissues to the liver for catabolism and excretion, higher serum
levels are considered protective against cardiovascular disease.
3-14. RISK FACTORS
Although high cholesterol levels are a risk factor for the development of
atherosclerosis, it is not the only risk factor. How aggressively the health care provider
decides to treat hyperlipidemia depends on the patient's overall risk for developing
atherosclerosis (heart disease). In addition to hyperlipidemia, the following are
significant risk factors:
a. Uncontrollable Risk Factors. These include age (greater than 45 for males
and greater than 55 for females), sex (male), and family history of premature coronary
heart disease (MI, stroke, or sudden death before age 55 in a male parent or sibling, 65
in a female parent or sibling).
b. Controllable Risk Factors. These include active tobacco smoking,
hypertension (treated or untreated), diabetes, severe obesity (>30% overweight),
physical inactivity, and Type A personality traits.
NOTE: A high HDL (>60 mg/dl) is actually considered a negative risk factor. This
means one positive risk factor may be subtracted in overall risk assessment. When
determining treatment, two or more risk factors are considered significant.
The treatment of hyperlipidemia depends on two factors: 1) whether that patient
has existing atherosclerosis and 2) the patient's other risk factors for atherosclerosis.
The treatment goal is usually expressed at the Low-density Lipoprotein (LDL) goal as
this is the major carrier of cholesterol in the blood.