A number of human studies examining the role of local factors in the pathogenesis of osteoporosis have been completed but the results are inconclusive. Several studies in humans, as well as in animals, suggest that several factors may alter cytokine activity in bone and these factors need to be more clearly examined. Few studies have looked at multiple local factors concurrently. This study is a pilot study to examine the effect of estrogen withdrawal on local factors in bone and to compare these changes with changes in bone turnover. There are three specific aims: 1) to examine the hypothesis that short-term estrogen withdrawal will alter cytokine expression in bone of older postmenopausal women; 2) to examine the hypothesis that short-term estrogen withdrawal will alter cytokine production in peripheral blood of older postmenopausal women; and, 3) to compare changes in biochemical markers of bone turnover with changes in cytokine expression.