Difference in effective dosage of genistein on bone and uterus in ovariectomized mice

Phytoestrogen including soybean isoflavones has structural similarity to es trogen and exhibits beneficial effects on bone tissue to protect against bo ne loss under estrogen-deficient conditions. Recent studies also indicate a possible action of isoflavones as endocrine disrupters in reproductive tis sues. In this study, we administered various dosages of genistein to ovarie ctomized (OVX) mice, and compared the effective dosages of genistein on bon e and uterus. Treatment with genistein at 0.7 mg/day prevented trabecular b one loss in OVX mice without hypertrophic effects on the uterus, while admi nistration of 5 mg/day of genistein induced uterine hypertrophy. The serum levels of genistein in OVX mice treated with 0.7 mg/day and 5 mg/day were 3 -fold (1.3 nmol/ml) and 50-fold (20.4 nmol/ml) higher than that in OVX mice . These results suggest that there is a marked difference between genistein dosages that protect against bone loss and those that induce uterine hyper trophy. (C) 2000 Academic Press.