Objective To determine the effects of soy-derived isoflavones on vaginal epithelium and the endometrium. Design Double-blind, randomized, placebo-controlled crossover trial. Setting Outpatient clinic of a university hospital. Patient(s) Sixty-four postmenopausal women with a history of breast cancer. Intervention(s) The women took (in a randomized order) 114 mg of isolated isoflavonoids or placebo in tablets daily for 3 months; the treatment regimens were crossed over after a 2-month washout period. The subjects were studied before and on the last day of each treatment period. Main outcome measure(s) Vaginal dryness, maturation index (MI) of vaginal epithelium, endometrial thickness, histology, and expression of estrogen (E) and progesterone (P) receptors and the proliferation marker Ki-67 in the endometrium. Result(s) Isolated isoflavones did not relieve vaginal dryness. Maturation index values remained unchanged during the isoflavone regimen, but decreased during the placebo regimen. No changes were found in any of the variables measured in the endometrium. Conclusion(s) Daily administration of 114 mg of isolated isoflavones for 3 months had no effect on the subjective perception of vaginal dryness or on objective findings in the vagina or endometrium. This implies safety with regard to the endometrium.
