Prolonged inhibition of placental and ovarian 3β-hydroxysteroid dehydrogenase during pregnancy and the luteal phase of the menstrual cycle

Summary The effects of a competitive inhibitor of 3β-hydroxysteroid dehydrogenase (3β-HSD), Epostane (Sterling Winthrop) on serum progesterone, oestradiol and Cortisol have been studied in twenty women who were awaiting termination of pregnancy and thirteen women in the luteal phase (days 19-21) of their menstrual cycle. In the pregnant women there was a highly significant decline in the mean serum progesterone concentration to 13-Onmol/litre (19 percent of the pretreatment value) after 4 days of treatment. A similar fall in serum oestradiol was observed. Progressive uterine activity did not occur in association with these changes. In the luteal phase study there was also a significant decline in serum progesterone to 13 per cent of the pretreatment value and this was accompanied by uterine bleeding, in 6 of 8 patients. The mean serum oestradiol concentration did not change. This treatment did not produce any adverse side effects and the mean serum Cortisol concentrations in both studies did not differ from those of the controls. Epostane is an effective inhibitor of placental and ovarian 3β-HSD, and may have an important clinical role as an interceptive agent.