•  
  • Age: male ≥ 45 years, female ≥ 55 years
  • Family history: coronary heart disease (CHD) in a male first-degree relative < 55 years or female first-degree relative < 65 years
  • Current cigarette smoking
  • Hypertension (≥ 140/90 mmHg or on antihypertensive medications)
  • Low HDL cholesterol: < 40 mg/dL (Note: High HDL-c is a negative risk factor; if the patient has a level > 60 mg/dL, subtract one risk factor.)

Reference: Larson PR, et al: Williams Textbook of Endocrinology, 10th ed. Philadelphia, W.B. Saunders, 2003.

Current recommendations for screening and treatment are based on the National Cholesterol Education Program guidelines that were last revised in 2001. It is recommended that adults 20 years or older have a screening fasting lipid profile obtained every 5 years (more often if they are at high risk). Treatment is based on determining the patient’s LDL cholesterol (LDL-c) goal. This goal is modified by cardiovascular risk factors (independent of LDL levels). 

Reference: Basa ALP, Afsharkharaghan H (Zollo A, ed): Endocrinology in Medical Secrets, 3rd ed. 2001.

Treatment is aimed at reducing triglyceride levels and may require fasting to lower the triglyceride levels into a safer range. 

Reference: Basa ALP, Afsharkharaghan H (Zollo A, ed): Endocrinology in Medical Secrets, 3rd ed. 2001.

Physical manifestations of this syndrome include lipemia retinalis, eruptive xanthomas, and hepatomegaly. Patients are at increased risk of developing pancreatitis. 

Reference: Basa ALP, Afsharkharaghan H (Zollo A, ed): Endocrinology in Medical Secrets, 3rd ed. 2001.

The chylomicronemia syndrome typically occurs when triglyceride levels are > 1000 mg/dl. Patients develop severe triglyceride elevations when the enzyme lipoprotein lipase (LPL), which is responsible for triglyceride hydrolysis of chylomicrons and very low density lipoprotein (VLDL), becomes saturated and is no longer able to clear chylomicrons from the circulation. When the LPL enzyme becomes saturated, chylomicrons accumulate, and the patient’s serum becomes lipemic. Severe chylomicronemia typically develops in patients with a combined genetic and acquired cause of hypertriglyceridemia. 

Reference: Basa ALP, Afsharkharaghan H (Zollo A, ed): Endocrinology in Medical Secrets, 3rd ed. 2001.

FH is an autosomal dominant disorder due to a mutation in the LDL receptor (causing a deficient or defective receptor) that leads to altered LDL catabolism and increased cholesterol synthesis. Approximately 1/500 people are heterozygous carriers of a mutation and 1/1,000,000 are homozygous for the disorder. Such people have much higher rates of premature atherosclerosis and can have myocardial infarctions at a very young age. Physical exam often reveals tendinous xanthomas (cholesterol deposition in the extensor tendons) and corneal arcus. Management is aimed at aggressive LDL-lowering to reduce cardiovascular risk.

Reference: Larson PR, et al: Williams Textbook of Endocrinology, 10th ed. Philadelphia, W.B. Saunders, 2003.

Lipoproteins are named based on their density and are composed of nonpolar (and therefore water-insoluble) cholesterol esters and triglycerides surrounded by a layer of polar (and therefore water-soluble) proteins and lipids (unesterified cholesterol and phospholipids). This structure allows the entire particle to remain miscible in serum.

LIPOPROTEIN PARTICLES

Lipoprotein Particle	Location of Origin	Composition	Apoproteins	Associated Disorders
Chylomicron	Intestine	80-95% TG	Apo B48	Chylomicronemia
		3-7% chol
VLDL	Liver	50-65% TG	Apo B100	Familial hyper triglyceridemia
		20-30% chol
				Familial combined hyperlipidemia
Remnants and IDL	Catabolism ofVLDL & chylomicrons	30-40% TG 30-50% chol	Depends on particle of origin	Familial dysbeta-lipoproteinemia (Broad beta disease)
LDL	IDL, VLDL remnants	4-10% TG 45-55% chol	B-100	Familial hypercholesterolemia,
				Familial combined hyperlipidemia
HDL	Liver, intestine	3-7% TG 25% chol	Apo A	Tangier’s disease

VLDL = very low density particle, LDL = low-density particle, ID = intermediate density particle, HDL = high-density particle, TG = triglycerides, chol = cholesterol.

Reference: American Heart Association: www.americanheart.org