- When is cholesterol screening done?
Although no protocol is universally accepted, measurement of total cholesterol and
high-density lipoprotein (HDL) cholesterol every 5 years once a person turns 20 years old
is considered reasonable by most authorities. Start sooner and screen more frequently
for obese patients and patients with a family history of hypercholesterolemia. - What physical findings will the Step 2 test use as clues to
hypercholesterolemia?
Xanthelasma (Fig. 5-1), tendon xanthomas (cholesterol deposits in the skin, classically over
tendons in the lower extremities), corneal arcus in younger patients, “milky”-appearing serum,
and obesity are possible markers for familial hypercholesterolemia. Family members should
be tested if a case of familial hypercholesterolemia is found. Pancreatitis in the absence of
obvious risk factors may be a marker for familial hypertriglyceridemia. - What are the current recommendations for management of cholesterol levels?
The following information is from the Third Report of the National Cholesterol Education Panel,
Adult Treatment Panel III (ATP III). Total cholesterol goal is less than 200 mg/dL with more
than 240 considered high, and normal triglycerides levels are less than 150 mg/dL with more
than 200 considered high, but LDL is usually the main player for treatment decisions. The
numbers in the chart below represent mg/dL: - List the major risk factors for coronary heart disease.
Although elevated levels of LDL and total cholesterol are risk factors for CHD, do not count
them as risk factors when deciding to treat or not to treat high cholesterol. The following
factors should be counted:
n Age (men aged 45 years and older; women aged 55 years and older or with premature
menopause and no estrogen replacement therapy)
n Family history of premature heart attacks (defined as definite myocardial infarction
or sudden death in father or first-degree male relative less than 55 years old or mother or
first-degree female relative less than 65 years old)
n Cigarette smoking
n Hypertension (greater than or equal to 140/90 mm Hg or prescription for antihypertensive
medications)
n Diabetes mellitus
n Low HDL (less than 40 mg/dL)
Note: An HDL level greater than or equal to 60 mg/dL is considered protective and negates
one risk factor. - Discuss other possible risk factors for heart disease.
C-reactive protein and homocysteine are hot topics right now, but ATP III does not list elevated
CRP or homocysteine as major risk factors for coronary artery disease. Obesity and type A
personality (the hard-driving attorney) are weaker risk factors, as are stress and physical
inactivity. Hypertriglyceridemia alone is not a significant risk factor but in association with high
cholesterol causes more coronary heart disease than high cholesterol alone. For Step 2 boards,
use only the definite risk factors mentioned in the previous question (especially when deciding
how to treat a patient with high cholesterol), but keep these other factors in mind. - How is LDL calculated?
Lipoprotein analysis involves measuring total cholesterol, HDL, and triglycerides. LDL then can
be calculated from the following formula:
LDL ¼ total cholesterol HDL (triglycerides/5) - Describe the treatment for hypercholesterolemia.
As with hypertension, give patients a few months to try lifestyle modifications (decreased
calories, cholesterol, and saturated fat in diet; decreased alcohol and smoking; exercise and
weight loss) before initiating drug therapy. If the patient has coronary artery disease or a
coronary artery disease equivalent (e.g., diabetes, peripheral vascular disease) and the LDL is
greater than or equal to 100, medication therapy is indicated. Once the decision to start
medications is made, first-line agents are HMG CoA reductase inhibitors (statins); watch for
Figure 5-1. Xanthelasma is usually a
normal finding with no significance but is
classically seen on the USMLE because of
its association with hypercholesterolemia.
Screen affected patients with a fasting
lipid profile. (From du Vivier A: Atlas of
Clinical Dermatology, 3rd ed. New York,
Churchill Livingstone, 2002, p 523, with
permission.)
CHAPTER 5 CHOLESTEROL 51
rare but potentially serious side effects (liver and muscle damage). Second line agents include
niacin (poorly tolerated, but effective and raises HDL), ezetimibe (selectively inhibits the
intestinal absorption of cholesterol), and bile acid-binding resins (e.g., cholestyramine). - How is HDL affected by alcohol? Estrogens? Exercise? Smoking?
Progesterone?
High HDL is protective against atherosclerosis and is increased by moderate alcohol
consumption (1 to 2 drinks/day; but not by high alcohol intake), exercise, and estrogens.
HDL is decreased by smoking, androgens, progesterone, and hypertriglyceridemia. - What causes hypercholesterolemia?
Genetics certainly plays a role (e.g., familial hyperlipidemia), but most cases are thought to be
multifactorial. Western diet and inactive lifestyle certainly contribute. Secondary causes of
increased cholesterol include uncontrolled diabetes, hypothyroidism, uremia, nephrotic
syndrome, obstructive liver disease, excessive alcohol intake (which increases triglycerides),
and medications (e.g., birth control pills, glucocorticoids, thiazides, beta blockers). - Why is cholesterol so important?
Cholesterol is one of the main known modifiable risk factors for atherosclerosis.
Atherosclerosis is involved in about one-half of all deaths in the United States and one-third
of deaths between the ages of 35 and 65 years. Atherosclerosis is the most important
cause of permanent disability and accounts for more hospital days than any other illness