The effects of androgens and cortisol on the in vivo metabolism of oestradiol.

We have examined the effect of co-administration of dehydroepiandrosterone sulphate, 5-androstenediol or cortisol on the metabolic clearance rate of oestradiol (MCR-E2) and conversion of oestradiol to oestrone (CRE2E1). Previous studies have shown that these androgens influence the metabolism of oestradiol in vitro while cortisol alters the distribution of oestradiol in plasma. The MCR-E2 and CRE2E1 were measured after 2.5 and 5 h of [3H]oestradiol infusion with co-infusion of androgen or cortisol starting after 2.5 h of tracer infusion. For one subject who did not receive co-infusion of another steroid no significant change in MCR-E2 or CRE2E1 occurred over the 5-h period. For other subjects, however, the MCR-E2 decreased by 18 +/- 7% (mean +/- SD) while the CRE2E1 increased by 45 +/- 12%. It is possible that these results are due to: changes in the distribution of oestradiol in plasma; differences in the metabolism of oestradiol bound to albumin or SHBG, or an effect of androgens or cortisol on the uptake of [3H]oestradiol by the liver.