Effects of Teriparatide, Alendronate, or Both in Women with Postmenopausal Osteoporosis

Context: Teriparatide increases both bone formation and bone resorption. Objective: We sought to determine whether combining teriparatide with an antiresorptive agent would alter its anabolic action. Design and Setting: This was a randomized controlled trial conducted in a single university hospital. Patients and Intervention: We randomized 93 postmenopausal women with low bone mineral density (BMD) to alendronate 10 mg daily (group 1), teriparatide 40 mu g sc daily (group 2), or both (group 3) for 30 months. Teriparatide was begun at month 6. Main Outcome Measures: BMD of the lumbar spine, proximal femur, proximal radius, and total body was measured by dual-energy x-ray absorptiometry (DXA) every 6 months. Lumbar spine trabecular BMD was measured at baseline and month 30 by quantitative computed tomography. Serum osteocalcin, N-terminal propeptide of type 1 collagen, and N-telopeptide levels were assessed frequently. Women who had at least one repeat DXA scan on therapy were included in the analyses (n = 69). Results: DXA spine BMD increased more in women treated with teriparatide alone than with alendronate alone (18 +/- 11 vs. 7 +/- 4%; P < 0.001) or both (18 +/- 11 vs. 12 +/- 9%; P = 0.045). Similarly, femoral neck BMD increased more in women treated with teriparatide alone than with alendronate alone (11 +/- 5 vs. 4 +/- 4%; P < 0.001) or both (11 +/- 5 vs. 3 +/- 5%; P < 0.001). Quantitative computed tomography spine BMD increased 1 +/- 7, 61 +/- 31, and 24 +/- 24% in groups 1, 2, and 3 (P < 0.001 for all comparisons). Serum osteocalcin, N-terminal propeptide of type 1 collagen, and cross-linked N-telopeptides of type I collagen increased more with teriparatide alone than with both (P < 0.001 for each marker). Conclusion: Alendronate reduces the ability of teriparatide to increase BMD and bone turnover in women. (J Clin Endocrinol Metab 95: 1838-1845, 2010)