A comparison of the effects of raloxifene and estrogen on bone in postmenopausal women

Raloxifene HCl, a selective estrogen receptor modulator, has been shown to increase bone mineral density (BMD) and decrease biochemical markers of bon e turnover in postmenopausal women without stimulatory effects on the breas t and uterus. However, it is not known whether the changes in BMD and bone turnover are associated with changes at the tissue level, nor how changes w ith raloxifene compare with estrogen. In this randomized, double blind stud y, we evaluated the effects of raloxifene (Evista, 60 mg/day) or conjugated equine estrogens (CEE; Premarin, 0.625 mg/day) on bone architecture, bone turnover, and BMD. Iliac crest bone biopsies were obtained at baseline and at the end of the study after double tetracycline labeling and were analyze d for standard histomorphometric indexes. Serum and urinary biochemical mar kers of bone turnover were measured at baseline and at 4, 10, 18, and 24 we eks of treatment. Total body, lumbar spine, and hip BMD were measured at ba seline and at the end of the study by dual energy x-ray absorptiometry. Act ivation frequency and bone formation rate/bone volume were significantly de creased from baseline in the GEE, but not in the raloxifene, group. Bone mi neralization did not change in either group. Most markers of bone resorptio n and formation decreased in both groups, but to a greater degree in the CE E group (P <.05). Total body and lumbar spine BMD increased from baseline i n both groups, with a greater increase in the CEE group (P < 0.05). Hip BMD significantly increased from baseline in the raloxifene group, but the cha nge was not different from that in the CEE group. These results suggest tha t raloxifene reduces bone turnover and increases bone density, although to a lesser extent than GEE. Thus, raloxifene is an alternative to CEE for the prevention and treatment of osteoporosis in postmenopausal women.