Soy protein isolate with isoflavones does not prevent estradiol-induced endometrial hyperplasia in postmenopausal women: a pilot trial.

Objective: To test the hypothesis that soy protein isolate (SPI) with isoflavones opposes the proliferative effects of exogenous estradiol (E2) on the endometrium after menopause.

Design: Thirty-nine postmenopausal women were randomized to receive daily for 6 months either 0.5 mg E2 + placebo, 1.