Identification of 4-hydroxyestriol in pregnancy urine

After enzymatic hydrolysis and various chromatographic steps, an estrogen metabolite behaving like 4-hydroxyestriol in capillary gas chromatography on several stationary phases was detected in pregnancy urine. The mass spectrum of its trimethylsilyl ether derivative showed the very characteristic fragmentation pattern of catechol estrogens and was found to be practically identical with that of the corresponding derivative of the reference standard. In addition, selected ion monitoring evidence of the identity of the new estrogen metabolite with 4-hydroxyestriol was obtained. It is concluded that the results confirm previous studies indicating formation of 4-hydroxylated estrogen metabolites in human tissues.