We evaluated and compared the effects of the phytoestrogen genistein, estrogen-progestogen therapy (EPT), and placebo on hot flushes and endometrial thickness in postmenopausal women.
Ninety healthy, postmenopausal women, 47 to 57 years of age, were randomly assigned to receive for 1 year continuous EPT (n = 30; 1 mg 17β-estradiol combined with 0.5 mg norethisterone acetate), the phytoestrogen genistein (n = 30; 54 mg/day), or placebo (n = 30). Endometrial safety was evaluated by intravaginal ultrasounds at baseline, 6 and 12 months.
By comparison with placebo, daily flushes reduced significantly by a mean of 22% (95% CI: −38 to −6.2; P < 0.01) after 3 months, by a mean of 29% (95% CI: −45 to −13; P < 0.001) after 6 months, and by a mean of 24% (95% CI: −43 to −5; P < 0.01) after 12 months of genistein treatment. Flush score decreased by a mean of 53% (95% CI: −79 to −26; P < 0.001) after 3 months, by a mean of 56% (95% CI: −83 to −28; P < 0.001) after 6 months, and by a mean of 54% (95% CI: −74 to −33; P < 0.001) after 12 months of EPT, as compared with placebo. No side effect was observed on the uterus of the participants.
The present study confirms that genistein might have positive effects on hot flushes without a negative impact on endometrial thickness and suggests a future role of this phytoestrogen as a strategically therapeutic alternative in the management of postmenopausal symptoms.