Enterohepatic recirculation of oestriol studied in cholecystectomized and non-cholecystectomized menopausal women

This study was done to evaluate the absorption of a single oral dose of 12 mg oestriol (Triovex, Leo AB, Sweden) and to confirm the hypothesis that the enterohepatic recirculation can prolong the plasma oestriol elevation obtained. Twelve menopausal women, six of whom had been cholecystectomized earlier, were given 12 mg oestriol orally. Fatty meals were given immediately after drug administration and then at four hourly intervals. Fat was given to induce the bileflow and provide oestriol to the intestine for deconjugation and enterohepatic recycling. One of the non-cholecystectomized women also remained fasting for 24 hours after oestriol administration. Plasma concentrations of unconjugated oestriol were measured by a specific RIA-method. In all women the plasma oestriol levels were considerably elevated for 24 hours. In the non-cholecystectomized women the plasma oestriol levels fluctuated in relation to meals whereas in the cholecystectomized women the fluctuations were not as pronounced, indicating that the release of biliary oestriol metabolites is the source of intestinal degradation and reabsorption to the systemic circulation. Fasting also gave increased and stable plasma oestriol levels. After a high oral dosage of oestriol, the enterohepatic recycling renders oestriol an enhanced potency since the plasma oestriol elevation time is prolonged.