EFFECTS OF HORMONAL THERAPIES AND DIETARY SOY PHYTOESTROGENS ON VAGINAL CYTOLOGY IN SURGICALLY POSTMENOPAUSAL MACAQUES

Objective: To evaluate the effects of conjugated equine estrogens, med roxyprogesterone acetate (MPA), conjugated equine estrogens combined w ith MPA, tamoxifen, and soybean estrogens on vaginal cytology in surgi cally postmenopausal cynomolgus macaques (Macaca fascicularis). Design : Randomized long-term experimental trial. Setting: Cytologic samples were taken from animals in two long-term randomized studies of the eff ects of hormonal and dietary effects on atherosclerosis. Patients: Sur gically postmenopausal cynomolgus macaques. Interventions: Conjugated equine estrogens, MPA, conjugated equine estrogens combined with MPA, tamoxifen, and soybean estrogens were given via the diet, at doses sca led from those given to women. Main Outcome Measure: Vaginal cytologic maturation index. Results: Conjugated equine estrogens elicited a mar ked maturation effect, which was antagonized partially by the addition of MPA. Tamoxifen produced a lesser estrogenic response. The cytologi c pattern in animals given soybean estrogens or MPA alone did not diff er from that of controls. Conclusion: Soybean estrogens at the doses g iven do not exert an estrogenic effect on the vagina of macaques. Conj ugated equine estrogens are potent inducers of vaginal keratinization in this model; tamoxifen has a lesser effect. Medroxyprogesterone acet ate partially antagonizes the effects of conjugated equine estrogens, and has no effect when given alone. The results support the possibilit y that soybean estrogens may be a ''tissue-selective'' estrogen with m inimal effects on the reproductive tract.