Oestrogen production and metabolism in peri-menopausal women.

The metabolic clearance rates and production rates of oestrone and oestradiol have been measured in a group of peri-menopausal women either with breast or endometrial cancer or having an increased risk of developing one of these diseases. The results were compared with values for normal post-menopausal women in whom the menopause was established. The transfer constants for the conversion of oestrone to oestradiol and of oestradiol to oestrone were also measured. Metabolic clearance rates for oestrone (1946 +/- 406 1/24 h) and oestradiol (1296 +/- 261 1/24 h) for peri-menopausal women, and production rates of oestrone (90 +/- 38 micrograms/24 h) and oestradiol (45 +/- 33 micrograms/24 h) were significantly higher than for normal post-menopausal women. Transfer constants for the conversion of oestrone to oestradiol and of oestradiol to oestrone were similar in the peri- and post-menopausal women. Plasma progesterone concentrations were less than 0.4 ng/ml in both groups of women. It is possible that the higher oestrogen production and clearance rates of peri-menopausal women, at a time when progesterone production is greatly reduced, may in part account for the higher risk that post-menopausal women have for developing breast or endometrial cancer.