All are impoant mechanisms in the formation of lithogenic bile:

Mechanisms in the formation of lithogenic (stone-forming) bile. The most impoant is increased biliary secretion of cholesterol. This may occur in association with obesity, the metabolic syndrome, high-caloric and cholesterol-rich diets, or drugs (e.g., clofibrate) and may result from increased activity of hydroxymethylglutaryl-coenzyme A (HMG-CoA) reductase. Reference: Harrisons Principles of Internal Medicine, 18th Edition, Page 2617