Synthesis of cholesterol

Actually about 80% of the body cholesterol is produced by your body itself and only 20% of cholesterol in the blood comes from your diet. About 20–25% of total cholesterol is produced by liver and the other regions where cholesterol is synthesized are the intestines, adrenal glands, and reproductive organs. Usually the synthesis of cholesterol within the body begins with a molecule of acetyl CoA and acetoacetyl-CoA. These two molecules get dehydrated and form 3-hydroxy-3-methylglutaryl CoA (HMG-CoA). This 3-hydroxy-3-methylglutaryl CoA (HMG-CoA) molecule is then reduced to mevalonate with the help of an enzyme called HMG-CoA reductase. 
Then mevalonate is converted into 3-isopentenyl pyrophosphate in three reactions, this conversion needs ATP. Then these three molecules are decarboxylated to three molecules isopentenyl pyrophosphate. After that these molecules are condensed to form farnesyl pyrophosphate by means of geranyl transferase. Then squalene is formed from two molecules of farnesyl pyrophosphate through the action of squalene. Then lanosterol is formed by the action of oxidosqualene cyclase. And finally, lanosterol is converted to cholesterol.