2-Year Therapy With Teriparatide vs 1-yr Therapy Followed by 1-Year of Raloxifene or Calcium/Vit D in Severe Postmenopausal Osteoporosis

Inclusion Criteria: * Ambulatory women greater or equal to 55 years, at least 2 years postmenopausal. * Lumbar spine or total hip or femoral neck bone mineral density measurement must be at least 2.5 standard deviations (SD) below the average bone mass for young women (T-score -2.5 or less). * Presence of at least one known and documented preexisting clinical fragility fracture, in the past 3 years. Patients may be included in substudy 2 if they meet any one of the following additional criteria - Patients who have sustained at least one new fragility fracture (vertebral or nonvertebral), despite prescription of antiresorptive therapy\* during the 12 months prior to the last new fracture or patients who, after a minimum of two years after initiating antiresorptive therapy\*, either have a lumbar spine, femoral neck, or total hip BMD of at least - 3SD below the average bone mass for young women (T-score -3 or less), or who show a decrease of at least 3.5% in BMD at any one of these sites. \*Antiresorptive therapy includes all bisphosphonates, raloxifene, ERT/HRT, calcitonin, and vitamin D metabolites. Exclusion Criteria: For substudy 1 patients only: * current or history of vaginal bleeding or spotting of unknown cause in the 1 year prior to study start * currently suspected or history of venous thrombotic events (VTE), including lower extremity thrombosis, and other major venous thromboses, or high risk of developing VTE as assessment by the investigator. Treatment with * Vitamin D \>50,000 IU/week or with any dose of calcitriol or vitamin D analogs or agonists in the 6 months prior to visit 2 * Fluorides in the 12 months prior to visit 2. * Systemic corticosteroids (other than for replacement therapy) in the 1 month prior to visit 2.(Ophthalmic, otic topical, orally inhaled, nasally inhaled, or intra-articular corticosteroid therapy may be used without these restrictions.)