Endocrine effects of tamoxifen in postmenopausal breast cancer patients

The effects of tamoxifen on plasma concentration of gonadotropins, prolactin (PRL), estrone (E1), estradiol-17 beta (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.