GH is important for the hepatic low density lipoprotein (LDL) receptor induction that occurs after estrogen treatment. GH treatment increases liver LDL receptors and lowers plasma LDL cholesterol in man. Estrogen treatment enhances biliary secretion of cholesterol, resulting in supersaturation of bile and an increased risk of gallstone formation. The present study was undertaken to investigate whether GH treatment also influences biliary lipid metabolism in humans. Twelve healthy male volunteers (mean age, 31 +/- 1 yr) were studied before and during the third week of treatment with recombinant human GH (0.1 IU/kg.day). Plasma lipids, bile acid kinetics, and biliary lipid composition were monitored. Plasma total and LDL cholesterol levels were reduced by 10% in response to therapy. However, no significant changes were observed in the biliary lipid composition or cholesterol saturation of gallbladder bile. Furthermore, there were no changes in chenodeoxycholic acid or cholic acid kinetics. The reduction of plasma LDL cholesterol in response to GH treatment in healthy adult men is not associated with detectable changes in biliary lipid metabolism. Thus, in contrast to estrogen, GH therapy of adults probably does not result in an increased risk of cholesterol gallstone development.