The distribution of oestradiol in plasma from postmenopausal women with or without breast cancer: Relationships with metabolic clearance rates of oestradiol

Abstract

The distribution of oestradiol in plasma from postmenopausal women with or without breast cancer has been measured and related to the metabolic clearance rates of oestradiol (MCR-E2). All measurements were carried out preoperatively. No difference in the free fraction of oestradiol was found between women with breast cancer (1.8 +/- 0.4%, mean +/- SD) and normal women (1.6 +/- 0.3%). Approximately 40% of oestradiol in plasma was bound to albumin with 60% bound to sex hormone binding globulin (SHBG), but values were similar for women with or without breast cancer. Concentrations of total unconjugated oestradiol and free oestradiol (2.4 +/- 0.5 ng/100 ml and 44 +/- 12 pg/100 ml respectively, mean +/- SD, n = 9) were significantly higher in plasma from postmenopausal women with breast cancer compared with levels in plasma from normal postmenopausal women (1.8 +/- 0.5 ng/100 ml and 27 +/- 10 pg/100 ml, n = 8). A significant correlation was found between the free oestradiol fraction and MCR-E2 (r = 0.53, p less than 0.05). Correlations were also found between the fractions of oestradiol bound to albumin and MCR-E2 (r = 0.45). From correlations between the binding capacity of SHBG and MCR-E2 it appears that, for a given level of SHBG, MCR-E2 may be higher in women with breast cancer.

Endogenous estrogens and breast cancer risk: the case for prospective cohort studies.

“…Siiteri's initial paper (31) reporting that free estradiol was elevated in postmenopausal breast cancer was followed by a number of similar case-control studies (21,26,30,(34)(35)(36)(37)(38)(39)(40)(41)(42). With some exceptions, (36,39,42) these studies appeared to confirm Siiteri's initial observations, but their overall impact was modest when it became evident that the observed association was not of sufficient strength to explain much of breast cancer epidemiology.…”

Hormones and Breast Cancer

“…There is considerable evidence that increased serum estrogen levels are associated with an increased risk of breast cancer in postmenopausal women (28)(29)(30)(31)(32)(33)(34)(35)(36)(37)(38); and increased urinary excretion rates of estrogen (estrone, estradiol and estriol conjugates) in postmenopausal breast cancer cases compared to controls have also been consistently found (39)(40)(41)(42)(43)(44)(45)(46). In addition to increased serum estrogen levels, it has also been suggested that the pathway by which estrone (El) is metabolized may be important in determining breast cancer risk (47)(48).…”

“…In an attempt to determine changes in cases-controls could obscure or They injected 33 peri-and postmenopausal whether an elevated ratio of 16cx-to accentuate the differences between these breast cancer patients and 10 postmeno-2-hydroxylation precedes diagnosis, groups. We addressed this issue by asking pausal controls with E 2 tracers labeled with Osborne and co-workers used radiometric participants whether they have changed 3 H in the 17(c, C-2, and 16ct position, methods to study estrogen metabolism in their diet in the past 10 years, and we will They drew serial blood samples before premenopausal women presumed to be at include a complete analysis of these data in a and after isotope administration and high or low risk of breast cancer (34). subsequent report on the completed study.…”