Secondary causes are far more common than primary causes and include all of the following: Chronic infections (including hepatitis C infection) and other inflammatory states Hematologic and other cancers Hyperthyroidism Malabsorption Undernutrition (including that accompanying chronic alcohol use) The unexpected finding of low cholesterol or low LDL-C in a patient not taking a lipid-lowering drug should prompt a diagnostic evaluation, including measurements of AST (aspartate aminotransferase), ALT (alanine aminotransferase), and thyroid-stimulating hormone; a negative evaluation suggests a possible primary cause.