II. Physiology
- See Lipoprotein
- HDL is synthesized in the liver as empty, non-lipid bound Proteins (apolipoprotein A1), starting as the smallest and most dense Lipoproteins
- HDL is a Cholesterol scavenger returns excess Cholesterol and LDL remnants back to the liver, for bile synthesis
- HDL also transports apolipoproteins C2 and E to and from Triglyceride rich Lipoproteins
- Lecithin-Cholesterol acyl transferase (LCAT) enzyme is bound to HDL
- LCAT converts free Cholesterol into the more hydrophobic Cholesterol esters that are then sequestered into Lipoproteins
III. Interpretation
- Positive Cardiac Risk Factor (Atherogenic)
- HDL < 35
- Total Cholesterol to HDL ratio
- Men > 5.0
- Women > 4.5
- Negative Cardiac Risk Factor (Protective)
- HDL > 60
IV. Increased
- Medications
- Gemfibrozil
- Niacin
- Exogenous Estrogens
- Moderate Alcohol intake (1 ounce per day)
- Regular aerobic Exercise
- Graded increase with miles run per week
- Kokkinos (1995) Arch Intern Med 155(4):415-20 [PubMed]
- Weight loss (for obese patients)
- HDL increases 2 mg/dl for each 4.5 kg of weight loss
V. Decreased
- Tobacco Abuse
- Diabetes Mellitus
- Hypertriglyceridemia
- Menopause
- Obesity
- Puberty in males
- Uremia
- Anabolic Steroids
- Apolipoprotein deficiency
- Liver disease
- Tangier disease
- Medications
- Progestins
- Probucol