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Relationship between Urine and Plasma Estrogen Ratios¹

Worcester Foundation for Experimental Biology, Shewsbury, Massachusetts 01545 [C. L.], and the Department of Medicine, Boston University School of Medicine, Boston, Massachusetts 02118 [C. L., J. H. P.]

Normal young and postmenopausal women were placed into groups according to the ratio of the estrogens in their urine. Women whose ratio was >1.3 if young and >3.2 if postmenopausal were compared to women whose ratio was <0.7 and <2.1 for young and postmenopausal, respectively. Between the respective high- and low-ratio groups, there were no significant differences for circulating levels of estriol, metabolic clearance rates of estriol, or blood production rates of estriol, estrone, or estradiol.

Women who had had breast cancer were compared to a group of normal controls and were also found to have similar blood production rates for estriol, estrone, and estradiol.

The ratios of the blood production rates of estriol to estrone and estradiol were similar for the high and low groups for young and postmenopausal women and also between the breast cancer women and their controls.

It appears, therefore, that the difference in urinary estrogen ratios is primarily due to different pathways of metabolism of the free circulating estrogens and not to differences in the production rates of the estrogens. Estriol is produced at only 10% the rate of estrone and estradiol.

¹ Presented at the John E. Fogarty International Center Conference on Hormones and Cancer, March 29 to 31, 1978, Bethesda, Md. Portions of this study were performed in the Clinical Research Center of Boston City Hospital, Boston University Division, which is supported by Grant RR-533 from the General Clinical Research Center's Program of the Division of Research Resources, NIH. The study was supported by Contract CB-33902 from the National Cancer Institute.

² To whom requests for reprints should be addressed.

³ Present address: Indiana University School of Medicine, Department of Medicine, 1100 West Michigan Street, Indianapolis, Ind. 46202.