Efficacy of red clover isoflavones in the menopausal rabbit model

Objective: To evaluate the effectiveness of phytoestrogens as alternatives for selective dysfunctional changes in the menopausal rabbit model. Design: Prospective, vehicle-controlled experimental study. Setting: Reproductive pharmacology laboratory in a university department. Animal(s): Twenty-four rabbits with experimentally induced menopause and six intact controls. Intervention(s): Surgical menopause was induced in 24 rabbits by ovariectomy. After 4 weeks of convalescence, three groups (n = 6) were given 100 mu g/kg E-2 valerate, 100 mu g/kg daidzein, or 6.68 mg/kg red clover extract daily for 12 weeks. The remaining six rabbits served as the operated control group. Main Outcome Measure(s): Vaginal blood flow using Doppler flowmetry, before, during, and after pelvic nerve stimulation; and measured parameters of uterine weight, femoral bone density, clitoral cavernosal histology, and hormone levels. Result(s): After pelvic nerve stimulation, blood flow increased remarkably in the daidzein-treated group. Serum E-2 and uterine weight increased significantly in the estrogen group. Cavernosal structure was well preserved in all three treatment groups, and bone mineral density was lowest in ovariectomized controls (0.3467 g/cm(2)) and highest in the red clover (0.4012 g/cm(2)) groups. Conclusion(s): Supplementing isoflavones for menopause leads to significant improvements in bone density, tissue integrity, and vaginal blood flow with minimal effect on uterine weight and may therefore be a viable alternative to conventional regimens using synthetic estrogens. (Fertil Steril(R) 2009;92:2008-13. (C)2009 by American Society for Reproductive Medicine.)