The Optimal Sequential Therapy After Long Term Denosumab Treatment

Inclusion Criteria: 1. Postmenopausal women or men over 50 years old 2. Continuous Denosumab treatment for at least three years (up to six doses). Exclusion Criteria: 1. Secondary osteoporosis 2. Metabolic bone diseases 3. Active or prior malignancy 4. Ongoing systemic glucocorticoid therapy 5. Current use of hormone replacement therapy 6. Current use of any medication known to affect bone metabolism 7. Prior use of any osteoporosis medication other than denosumab 8. Estimated glomerular filtration rate (eGFR) \< 40 mL/min 9. Known hypersensitivity to zoledronic acid 10. Hypocalcemia 11. Any other contraindication to zoledronic acid 12. Age \> 85 years 13. Esophageal abnormalities that delay esophageal emptying (e.g., esophageal stricture, achalasia) 14. Inability to stand or sit upright for at least 30 minutes