Endocrine Effects of Tamoxifen in Postmenopausal Breast Cancer Patients

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Abstract
The effects of tamoxifen on plasma concentration of gonadotropins, prolactin (PRL), estrone (E1), estradiol-17β (E2), and sex hormone-binding globulin (SHBG) were studied in 40 postmenopausal breast cancer patients. In addition, the changes induced by the drug on endometrium and vaginal epithelium were investigated. After 6–8 weeks of tamoxifen treatment, a significant decrease in FSH, LH and PRL basal levels was observed, whereas the concentrations of E1 and E2 were not significantly affected. A significant increase in SHBG levels was induced by prolonged treatment with the drug. In addition, tamoxifen caused a partial estrogenization of vaginal smears, and a weak stimulatory effect on endometrium was also apparent. These findings indicate that tamoxifen produced agonistic effects on some targets and antagonistic effects on the others.