Changes in OPG-Fc-FITC fluorescence as an index of mean RANKL surface concentration per cell (mean ± SEM). The premenopausal women (Group A) are shown by the white bars, the untreated postmenopausal women (Group B) by gray bars, and the estrogen-treated postmenopausal women (Group C) by black bars. There is a highly significant (ANOVA P values as indicated) difference among three groups. There is a two- to threefold significant increase of the mean RANKL fluorescence intensity per cell in Group B over Group A (*) and a somewhat smaller significant increase in Group B over Group C (**) as analyzed by the Student-Newman-Keuls test.