Increased urinary catechol estrogen excretion in female smokers

Abstract

Premenopausal female smokers show significantly increased estrogen 2-hydroxylation, which may account in part for the anti-estrogenic effects of cigarette smoking. We have measured five major urinary estrogens, including estradiol (E 2), estrone (E 1), 16α-hydroxyestrone (16αOHE 1), estriol (E 3), and 2-hydroxyestrone (2OHE 1), in premenopausal female smokers and non-smokers, to determine whether increased C-2 hydroxylation affected the urinary excretory patterns in these subjects. While total measured estrogen excretion in the follicular phase did not differ significantly between the two groups, urinary 2OHE 1 among the smokers constituted a significantly greater proportion of the total (31.1 vs 18.2%, P < 0.02). This difference was largely caused by significantly increased urinary 2OHE 1 and decreased E 3 observed in smokers. A urinary catechol estrogen index, defined by [2OHE 1] [E 3] , was significantly elevated in smokers compared with non-smokers (1.67 ± 0.21 vs 0.56 ± 0.08, P<0.001), and this urinary index correlated strongly with radiometrically determined estrogen 2-hydroxylation ( r=0.84, P <0.01). Ratios of the various estrogen metabolites did not vary substantially throughout the menstrual cycle. Urinary estrogen indices as described here may therefore be useful in demonstrating differences in estrogen metabolism, specifically 2-hydroxylation vs 16α-hydroxylation, in selected populations.