This study intends to investigate whether Alendronate and Zoledronate can prevent bone mineral density loss after long-term treatment with Denosumab.

This study intends to use a randomized trial to test whether Alendronate and Zoledronate can avoid the risk of rapid bone loss after the withdrawal of Denosumab.

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

after application