Metabolic clearance rate of oestrone sulphate in post-menopausal women

The feasibility of using constant infusions of unlabelled oestrone sulphate (E1S) for the purposes of calculating its metabolic clearance rate (MCRE1S) and its conversion ratios to oestrone (E1) and oestradiol (E2) in post-menopausal women was exploited in this study. The results obtained by the infusion of unlabelled E1S were similar to those obtained by the infusion of labelled steroid. The MCRE1S values seen in our group of post-menopausal women fell within the range previously reported for fertile women. The contribution of E1S to circulating E1 averaged 18% (range 14-24%), indicating that the E1S-E1 equilibrium should be taken into account during studies on oestrogen balance in post-menopausal women.