Bone Effects of Teriparatide Following Alendronate

Inclusion Criteria: * Diagnosis of Osteoporosis: Pretreated patients currently osteoporotic or osteopenic. Treatment-naive patients currently osteoporotic * Pretreated patients will have had at least 36 months of treatment with alendronate Na 10 mg/day or 70 mg/week. Treatment-naive patients will have no significant osteoporosis treatment in the prior 36 months, as assessed by the investigator Exclusion Criteria: * History of bone metabolic diseases, Paget's disease, renal osteodystrophy, osteomalacia, any secondary causes of osteoporosis, hyperparathyroidism (uncorrected), and intestinal malabsorption. * History of malignant neoplasms in the prior 5 years, with the exception of superficial basal cell carcinoma or squamous cell carcinoma of the skin that has been definitively treated. If malignant neoplasm was ever diagnosed, patient must presently be free of disease.