Secondary causes of high HDL-C include all of the following: Alcohol use disorder without cirrhosis Hyperthyroidism Primary biliary cirrhosis Medications (eg, corticosteroids, insulin, phenytoin, estrogen) The unexpected finding of high HDL-C in patients not taking lipid-lowering drugs should prompt a diagnostic evaluation for a secondary cause with measurements of AST (aspartate aminotransferase), ALT (alanine aminotransferase), and thyroid-stimulating hormone; a negative evaluation suggests a possible primary cause.