Estrogen-replacement therapy prevents osteoporosis in postmenopausal women by inhibiting bone resorption, but the balance between its long-term risks and benefits remains unclear. Whether other antiresorptive therapies can prevent osteoporosis in these women is also not clear. We studied the effect of 2.5 mg or 5 mg of alendronate per day or placebo on bone mineral density in 1174 postmenopausal women under 60 years of age. An additional 435 women who were prepared to receive a combination of estrogen and progestin were randomly assigned to one of the above treatments or open-label estrogen–progestin. The main outcome measure was the change in bone mineral density of the lumbar spine, hip, distal forearm, and total body measured annually for two years by dual-energy x-ray absorptiometry. The women who received placebo lost bone mineral density at all measured sites, whereas the women treated with 5 mg of alendronate daily had a mean (±SE) increase in bone mineral density of 3.5±0.2 percent at the lumbar spine, 1.9±0.1 percent at the hip, and 0.7±0.1 percent for the total body (all P<0.001). Women treated with 2.5 mg of alendronate daily had smaller increases in bone mineral density. Alendronate did not increase bone mineral density of the forearm, but it slowed the loss. The responses to estrogen–progestin were 1 to 2 percentage points greater than those to the 5-mg dose of alendronate. Alendronate was well tolerated, with a safety profile similar to that of placebo or estrogen–progestin. Alendronate prevents bone loss in postmenopausal women under 60 years of age to nearly the same extent as estrogen–progestin.

Thinness (low percentage of body fat, low body mass index [BMI], or low body weight) was evaluated as a risk factor for low bone mineral density (BMD) or increased bone loss in a randomized trial of alendronate for prevention of osteoporosis in recently postmenopausal women with normal bone mass (n = 1609). The 2‐year data from the placebo group were used (n = 417). Percentage of body fat, BMI, and body weight were correlated with baseline BMD (r = −0.13 to −0.43, p < 0.01) and 2‐year bone loss (r = −0.14 to −0.19, p < 0.01). Women in the lowest tertiles of percentage of body fat or BMI had up to 12% lower BMD at baseline and a more than 2‐fold higher 2‐year bone loss as compared with women in the highest tertiles (p ≤ 0.004). Women with a lower percentage of body fat or BMI had higher baseline levels of urine N‐telopeptide cross‐links (r = −0.24 to −0.31, p < 0.0001) and serum osteocalcin (r = −0.12 to −0.15, p < 0.01). To determine if the magnitude of treatment effect of alendronate was dependent on these risk factors, the group treated with 5 mg of alendronate was included (n = 403). There were no associations between fat mass parameters and response to alendronate treatment, which indicated that risk of low bone mass and increased bone loss caused by thinness could be compensated by alendronate treatment. In conclusion, thinness is an important risk factor for low bone mass and increased bone loss in postmenopausal women. Because the response to alendronate treatment is independent of fat mass parameters, prevention of postmenopausal osteoporosis can be equally achieved in thinner and heavier women.

Preventing bone loss associated with menopause and aging and maintaining the normal micro-architecture of bone provide important opportunities for the prevention of osteoporosis and fractures. To determine the safety and efficacy of alendronate, an aminobisphosphonate, for preventing postmenopausal bone loss. 3-year double-blind, randomized, placebo-controlled trial. 15 osteoporosis centers throughout the world. 447 women who had recently experienced menopause (6 to 36 months before study entry). Participants were randomly assigned to one of five regimens: oral placebo; oral alendronate, 1, 5, or 10 mg/d; or oral alendronate, 20 mg/d for 2 years followed by placebo during the third year (20/0 mg/d). Bone mineral density was measured by dual-energy x-ray absorptiometry. Bone turnover and bone quality were assessed with biochemical markers and bone histomorphometry. Alendronate at 5, 10, and 20/0 mg/d increased bone mineral density from baseline at the lumbar spine, femoral neck, and trochanter by 1% to 4% and in the total body by 0.3% to 1.0%; placebo led to losses of 2% to 4% at these sites. Alendronate, 1 mg/d, attenuated losses relative to those seen with placebo. Alendronate decreased markers of bone resorption to a new steady state by 3 months and decreased markers of bone formation by 6 to 12 months. Bone quality remained normal. At all dosages studied, alendronate had a safety and tolerability profile similar to that of placebo. In early postmenopausal women, alendronate given for 3 years at dosages of 5 mg/d or greater prevented the loss of bone mineral density at the spine and hip and in the total body. Alendronate seems to be a safe and effective nonhormonal option for prevention of postmenopausal bone loss.

Up to 3 years of treatment with alendronate, 5 mg/d, prevents postmenopausal bone loss. To determine whether the effect of alendronate is sustained at 4 years of treatment and persists after treatment is discontinued. Randomized, controlled trial. United States and Europe. 1609 postmenopausal women 45 to 59 years of age. Participants were randomly assigned to receive oral alendronate, 5 mg/d or 2.5 mg/d; placebo; or open-label estrogen–progestin. Women in the alendronate groups received alendronate for the first 2 years of the study. Treatment was then continued without change or replaced with placebo for the last 2 years of the study. Annual measurement of bone mineral density. By year 4, the bone mineral density of participants in the placebo group had decreased by 1% to 6% (P < 0.001). Four years of treatment with 5 mg of alendronate per day increased bone mineral density at the spine (mean change [±SE], 3.8% ± 0.3%), hip (mean, 2.9% ± 0.2%), and total body (mean, 0.9% ± 0.2%) (P < 0.001 overall). By year 4, bone mineral density at most skeletal sites was greater in participants who switched from alendronate to placebo than in those who continuously received placebo. In years 3 and 4, bone loss in participants who switched from alendronate to placebo was similar to that seen during years 1 and 2 in those who continuously received placebo. Compared with 5 mg of alendronate per day, estrogen-medroxyprogesterone acetate produced similar increases in bone mineral density and estradiol-norethisterone acetate produced increases that were substantially greater. Four years of treatment with alendronate or estrogen–progestin prevented postmenopausal bone loss. A residual effect was seen 2 years after alendronate therapy was stopped; however, continuous alendronate treatment was more effective in preventing postmenopausal bone loss than 2 years of alendronate followed by 2 years of placebo. *For members of the Early Postmenopausal Intervention Cohort Study Group, see Appendix.