Standard lipid analysis includes measuring serum or plasma total cholesterol, triglycerides, and high density lipoprotein cholesterol (HDL-C) after an overnight fast. Low density lipoprotein cholesterol (LDL-C) is then calculated. Our own prospective studies from the Framingham Offspring Study indicates that LDL-C, small dense LDL-C (sdLDL-C), lipoprotein(a) or Lp(a), and HDL particle measurements add significant information about cardiovascular disease (CVD) risk to the standard lipid profile. Common familial lipid disorders associated with premature CVD include Lp(a) excess, combined hyperlipidemia, and dyslipidemia. Plasma fatty acid analysis is important in order to assess adequacy of omega-3 fatty acid intake, and whether there are excess levels of saturated and trans fatty acids for dietary recommendations. Plasma sterol analysis can be helpful for the diagnosis of causes of elevated very low density lipoprotein (VLDL-C > 50 mg/dL) and/or LDL-C (> 160 mg/dL) which includes familial combined hyperlipidemia (elevated lathosterol), familial hypercholesterolemia (normal sterols), dysbetalipoproteinemia (moderate increases in β-sitosterol), phytosterolemia (very high β-sitosterol), and cerebrotendinous xanthomatosis (very high cholestanol). The measurement of apolipoprotein (apo) A-I in HDL particles by gel electrophoresis is important in assessing CVD risk, HDL functionality, and for the diagnosis of marked HDL deficiency states (HDL-C < 20 mg/dL due to apoA-I deficiency and variants, Tangier disease and lecithin:cholesteryl acyltransferase (LCAT) deficiency, as well as hepatic lipase and cholesteryl ester transfer protein deficiency. The measurement of apoB is important for the diagnosis of abetalipoproteinemia and hypobetalipoproteinemia. The definitive diagnosis of the above mentioned disorders along with causes of markedly elevated triglycerides (> 1,000 mg/dL) requires next generation DNA sequencing of the appropriate and relevant genes for these disorders in order to provide a definitive molecular diagnosis often necessary to formulate optimal therapy strategies. For complete coverage of this and all related areas of Endocrinology, please visit our FREE web-textbok, www.endotext.org.

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