Cholesterol, Total, Serum/Plasma

Cholesterol is an essential component of mammalian cells and is the precursor for the biosynthesis of bile acids as well as adrenal, pituitary, and sex hormones. Most cellular cholesterol resides in the plasma membrane and constitutes 35% to 45% of lipid molecules. Therefore, the level of plasma membrane cholesterol depends on the steady state of cholesterol between the cell surface and lipoproteins in the extracellular medium. Whole-body cholesterol homeostasis is largely mediated by the liver. Hepatic cholesterol is secreted in the lipoprotein form. Very low density lipoprotein (VLDL) and its product, LDL, contain a single copy of a large structural apolipoprotein known as apolipoprotein B-100 or ApoB. Cholesterol in LDL is available for delivery to the peripheral cells, where ApoB serves as the ligand for the specific endocytosis pathway mediated by the LDL receptor. The cholesterol delivered by the lipoprotein particle is then available for cell metabolism and suppresses endogenous cholesterol synthesis. Because the liver expresses its own LDL receptors, the same mechanism allows it to react to the circulating level of LDL.

Elevated cholesterol levels are a well-established risk factor for cardiovascular disease. High levels are seen in familial hyperlipidaemia type IIa and IIb, familial dys β- lipoproteinaemia, familial combined hyperlipidaemia, hyperlipidaemia types I, IV, V and hyperlipoproteinaemia, ischemic heart disease, hepatocellular disease, cholestasis, glomerulonephritis, nephrotic syndrome, renal failure, malignant neoplasm of the pancreas and prostate, hypothyroidism, diabetes, gout, alcoholism, glycogen storage disease type I, and others. Decreased levels are seen in β-lipoprotein deficiency, hypo and β- lipoproteinaemias, hepatocellular necrosis, malignant neoplasm of the liver, malabsorption, malnutrition, anaemia, Thalassemia, sever acute illness, and rheumatoid arthritis.

1 ml Serum 1 ml Li-Heparin or K3-EDTA Plasma Stability: 7 Days at 15-25 °C 7 Days at 2-8 °C 3 Months at (-15)-(-25) °C

12 hours fasting preferred. Use of EDTA plasma leads to slightly lower values.

Optimum: < 200 mg/dL < 5.18 mmol/L Borderline: 200 - 240 mg/dL 5.18 - 6.22 mmol/L High: > 240 mg/dL > 6.22 mmol/L