Cholesterol can be gained either from the diet or it can be synthesized de novo, mainly in the liver. Cholesterol is transported round the body in lipoprotein particles. The rate of synthesis of cholesterol is dependent on the cellular level of cholesterol. The High levels of cholesterol and its metabolites control cholesterol biosynthesis by:

-  Opinion-inhibiting the activity of HMG CoA reductase an enzyme that catalyzes the committed step in cholesterol biosynthesis;

-  Decreasing the amount of HMG CoA reductase by reducing the synthesis and translation of its mRNA;

-  Decreasing the amount of HMG CoA reductase by raising its rate of degradation.