Metabolism of estriol-17alpha-3H in man

Estriol stereospecifically labelled with tritium at the 17 α position was prepared and administered together with 14 C labelled estriol to three subjects including one cirrhotic. No significant tritium was present in the plasma or urine water and hence no oxidation at C-17 had occurred. Excretion of radioactivity was very rapid particularly in the cirrhotic subjects. Analysis of the enzyme and acid hydrolysates showed that they consisted of only three compounds. The majority of the excreted radioactivity consisted of estriol which did not lose any of the tritium at 17 α . The only other compounds were 16-ketoestradiol (0.8%) and 16-epiestriol (0.2%). Both metabolites retained the major part of the tritium at C-17 α and hence could not have arisen via 17-keto intermediates.