title: Enterohepatic circulation of vitamin D: a reappraisal of the hypothesis.
abstract: Vitamin-D metabolites in bile were investigated after oral and intravenous doses of radioactively labelled vitamin D had been given to six patients with T-tube biliary drainage after cholecystectomy. The vitamin was mainly excreted as highly polar inactivation products and less than 4% of the metabolites in bile were present as 25-hydroxyvitamin D or its glucuronide conjugate. There was insufficient vitamin D or 25-hydroxyvitamin D in bile for the reabsorption of these metabolites to make a significant contribution to normal vitamin-D status. Therefore interference with an enterohepatic circulation of vitamin-D metabolites cannot be a cause of vitamin-D deficiency.
mesh_terms: D000284:Administration, Oral; D000368:Aged; D001646:Bile / Q000378:metabolism*; D002112:Calcifediol / Q000378:metabolism; D002250:Carbon Radioisotopes; D002762:Cholecalciferol / Q000378:metabolism; D002763:Cholecystectomy; D004764:Enterohepatic Circulation; D005260:Female; D005966:Glucuronidase / Q000494:pharmacology; D006801:Humans; D007275:Injections, Intravenous; D008297:Male; D008875:Middle Aged; D014316:Tritium; D014807:Vitamin D / Q000008:administration & dosage / Q000378:metabolism*
chemical_list: D002250:Carbon Radioisotopes; D014316:Tritium; D014807:Vitamin D; D002762:Cholecalciferol; D005966:Glucuronidase; D002112:Calcifediol