Denosumab, Teriparatide or Both for the Treatment of Postmenopausal Osteoporosis

Inclusion Criteria: Must satisfy A and B and C and D below: * (A) Women aged \> 55 * (B) Postmenopausal * (C) Osteoporotic with high risk of fracture Exclusion Criteria: * Confirmed serum alkaline phosphatase above upper normal limit with no explanation * Liver disease (AST or ALT \> 2 x upper normal limit). * Renal disease (serum creatinine \> 2.0 mg/dl). * Hypercalcemia (Ca \>10.5 mg/dL) * Elevated blood PTH (intact PTH \> 65 pg/ml) * Serum 25-OH vitamin D \< 20 ng/ml * HCT \< 32%. * History of malignancy (except basal cell carcinoma) or radiation therapy. * Significant cardiopulmonary disease including unstable coronary artery disease, stage D ACC/AHA heart failure or any other condition that the investigator deems may preclude the subject from participating safely or completing the protocol procedures. * Major psychiatric disease that in the opinion of the investigator would preclude the subject from providing adequate informed consent or completing the protocol procedures. * Excessive alcohol use or substance abuse that in the opinion of the investigator would preclude the subject from providing adequate informed consent or completing the protocol procedures. * Known congenital or acquired bone disease other than osteoporosis (including osteomalacia, hyperparathyroidism, Paget's disease) * Current use or use in the past 6 months of oral bisphosphonate * Current use or use within the past 3 months of estrogens, selective estrogen receptor modulators, or calcitonin. * Use of oral or parenteral glucocorticoids for more than 14 days within the past 6 months. * Any current or previous use of strontium or any parenteral bisphosphonate. * Known sensitivity to mammalian cell-derived drug products. * Known sensitivity to teriparatide or any of its excipients.