Cholesterol is principally metabolized by the liver. Serum levels are controlled by the balance between blood uptake, cholesterol production and excretion in the intestine via bile acids. Low levels of cholesterol in the plasma may reflect an inherited deficiency of either LDL or HDL, or they may reflect impairment of liver function.
High levels can be categorized as
Primary: hereditary or genetic which causes a defect in lipid metabolism. Familial hypercholesterolaemia is the main cause of primary or genetic hypercholesterolaemia, and results in deficient uptake of LDL particles which accumulate in the blood stream.
Secondary: lifestyle such as poor diet, physical inactivity, increased weight and conditions producing secondary hyperlipidaemia, such as diabetes, hypothyroidism, chronic renal failure, chronic liver disease especially alcoholic, chronic biliary obstruction, primary biliary cirrhosis and certain drugs such as steroids, oestrogens.
Cholesterol correlates to the risk of cardiovascular disease and is a modifiable risk factor. Total cholesterol > 6.5mmol/L doubles the risk of Coronary Artery Disease (CAD) where as a level > 7.8mmol/L increases it fourfold. Reducing cholesterol by 20% reduces coronary risk by 10%. Lipid lowering therapy reduces the incidence of stroke and coronary artery disease. Lifestyle intervention must underpin all approaches in treatment.
The Irish heart foundation recommends the following targets:
Target Cholesterol and Triglycerides:
| Total cholesterol: | <5 mmol/l |
| LDL cholesterol: | <3 mmol/l |
| HDL cholesterol: | >1 mmol/l |
| Triglycerides: | < 2 mmol/l |
For people with heart disease or diabetes :
| Total cholesterol: | < 4.5 mmol/l |
| LDL cholesterol: | < 1.8 mmol/l |
There are several algorithms available to assess CVD risk and when to initiate treatment.
https://statindecisionaid.mayoclinic.org/index.php/statin/index?PHPSESSID=7t5s8vcrtmlilekvejb4pd91g4
https://academic.oup.com/eurheartj/article/41/1/111/5556353
https://www.escardio.org/Journals/ESC-Journal-Family/European-Journal-of-Preventive-Cardiology
