THE ABSORPTION AND METABOLISM OF ORAL OESTRADIOL, OESTRONE AND OESTRIOL

The absorption, metabolism and clearance of oestradiol, oestrone and oestriol from the peripheral circulation were investigated in five postmenopausal women after the oral administration of Hormonin (oestradiol 600 μg, oestrone 1400 μg, oestriol 270 μg) daily for five consecutive days. In addition the concentrations of plasma oestrone‐3‐sulphate, oestrone‐3‐glucuronide, LH and FSH were determined in the same plasma samples. The maximum concentrations of each steroid in peripheral plasma and the time intervals during which the peak occurred after ingestion of the last tablet were:—oestrone (750 to 2116 pmol/1, 0·5 to 6·0 hours), oestradiol (246 to 813 pmol/1, 1 to 8 hours), oestriol (173 to 241 pmol/1, 5 to 12 hours), oestrone‐3‐glucuronide (32·2 to 78·8 nmol/1, 0·5 to 3·0 hours) and oestrone‐3‐sulphate (21·9 to 39·0 nmol/1, 1 to 7 hours). The mean factorial increases in the concentration of each compound during the first 12 hours post‐treatment over the baseline values were:—oestrone (4·1); oestradiol (4·4); oestriol (1·7); oestrone‐3‐sulphate (2·6) and oestrone‐3‐glucuronide (8·1). After treatment, the concentration of plasma oestradiol remained significantly higher than the baseline values (p <0·025) for 24 hours and the values for each subject were within the normal range for premenopausal women. Moreover, there was a significant reduction (p < 0·025) in the level of circulating LH. It is concluded that the simultaneous administration of oestrone, oestradiol and oestriol, by mouth, to postmenopausal women is a good approach to maintaining an appropriate concentration of oestradiol in peripheral plasma.