Cigarette smoking and endogenous sex hormone levels in postmenopausal women

Background: Epidemiological evidence has suggested that cigarette smoking has an effect on estrogen and androgen levels in women, but the possible mechanisms are not yet fully understood. The aim of the present study was to investigate the effect of past and current smoking on the serum levels of total estrone, estradiol, androstenedione, testosterone, sex hormone binding globulin (SHBG), and prolactin in postmenopausal women differentiated by current use of hormone replacement therapy (HRT). Methods: Sex hormone concentrations were measured in 2,388 subjects (1,378 current HRT users, 1,010 HRT non-users) recruited as controls in a population-based case-control study of breast cancer (MARIE). Associations between log transformed hormone levels and smoking status were assessed separately in users of HRT and in non-users. Geometric mean concentrations were compared across levels of smoking using multiple linear regression to account for potential confounders, such as age, parity, BMI, alcohol intake, and type of menopause. Results: Current smokers had significantly higher adjusted geometric means for total estrone (51.7, 50.9, 47.7 pg/ml in current, former, never smokers), estradiol (19.9, 19.5, 18.1 pg/ml), androstenedione (1.2, 1.03, 1.1 pg/ml) and SHBG (44.7, 37.5, 37.6 nmol/l) concentrations and lower prolactin (4.4 5.1, 5.3ng/ml) concentrations compared to never smokers, in both HRT users and non-users (p<0.05). Total estrone and estradiol concentrations were also significantly higher among past smokers compared to never smokers. Testosterone concentrations (0.41, 0.37, 0.39ng/ml) were not associated with smoking status. Conclusion: These results confirm previous reports that current cigarette smoking increases total estrone, estradiol, androstenedione, and SHBG levels in postmenopausal women regardless of current HRT use. The lower prolactin levels could be explained by the inhibition of prolactin secretion by high levels of dopamine among smokers.