Inclusion Criteria:

1. Postmenopausal women who are 60 to 90 years of age.

2. With BMD T-score of lower than -2.5 at the lumbar spine or total hip and -4.0 or higher at both sites. Subject who also meet the following criteria:

   A arm:-Subject who meet National Health Insurance (NHI) reimbursement criteria for use of denosumab.

   B arm:-Subject who does not meet NHI reimbursement criteria for use of denosumab, or who is no willing to receive denosumab treatment during study period, even meet NHI reimbursement criteria.

3. Subject who are naïve to osteoporosis treatment or have received prior bisphosphonate treatment for less than 3 years and not within 12 months prior to screening visit.

4. A minimum of 2 evaluable lumbar vertebrae in the L1-L4 region and 1 evaluable hip (i.e., either the left or right side).

5. Willingness to limit additional Vitamin D3 intake to 400IU or 800IU per day during the study period.

6. Ability to complete the entire procedure and to comply with study instructions.

7. Will provide completed and signed written informed consent.

Exclusion Criteria:

1. Subjects who had conditions that influence bone metabolism (i.e., Paget's disease and osteomalacia).
2. Subject on other osteoporosis therapies, parathyroid hormone or its derivatives, corticosteroids, systemic hormone-replacement therapy, selective estrogen-receptor modulators, tibolone, calcitonin or calcitriol 6 weeks prior to screening visit.
3. Subjects had a serum 25-hydroxyvitamin D level of less than 12 ng/ml.
4. Subjects had a BMD T-score of less than -4.0 at the lumbar spine or total hip.
5. Subjects with any severe or more than two moderate vertebral fractures on spinal x-ray at screening visit.
6. Subject who plan to initiate a new bisphosphonate treatment during study period.
7. Known hypersensitivity to any component of the study drug product.
8. Participation in any other investigational study within 30 days prior to receiving study medication.
9. Any condition that in the opinion of the investigator would jeopardize the evaluation of efficacy or safety.