Eldecalcitol and Calcitriol in Postmenopausal Women With Low Bone Mineral Density or Mild Osteoporosis

Inclusion Criteria:

1. Postmenopausal women (based on medical history) aged 50 or older and menopause timemore than 2 years. If there is uncertainty regarding menopausal status, women 60years of age and older will be considered postmenopausal.

2. BMD (determined by DXA) of lumbar L1-4 or total hip or femoral neck met one of thefollowing conditions at screening:

1. low BMD: -2.5<T< -1.0, without vertebral and fragility fracture history 2) mildosteoporosis: T≤-2.5, without vertebral and fragility fracture history 3. Ambulatoryoutpatients 4. Written informed consent

Exclusion Criteria:

1. Severe vitamin D deficiency at screening (defined as serum 25OHD<10 ng/ml);Vitamin Drepletion will be permitted and dosage will be at the discretion of investigatorsand subjects may be re-screened

2. Primary hyperparathyroidism, Cushing's syndrome, hyperthyroidism, gonadalinsufficiency, osteogenesis impotence, rheumatoid arthritis, poorly controlleddiabetes mellitus (HbA1c>9%), or other conditions that can cause secondaryosteoporosis, or treatment with glucocorticoids in the 2 months prior to study entry

3. Had injected bisphosphonate once or more within 3 years before entering the study;or had received oral bisphosphonate oral for 6 months or more in the 3 years priorto study entry; or had received parathyroid hormone once or more in the 3 yearsbefore entering the study; or received 2 weeks or more of calcitonin or vitamin K oractive vitamin D or selective estrogen receptor modulator or hormone replacementtherapy or traditional Chinese medicine for bone pine within 2 months prior to studyentry; or received subcutaneous anti-RANKL antibody at any time prior to study entry

4. Urolithiasis at screening

5. Hypercalcemia (serum calcium >10.4 mg/dL), or hypercalciuria (urine calcium>400mg/gCr), or hyperuricemia (above 420 μmol/L in men and 360 μmol/L in women)

6. Severe liver disease such as cirrhosis or serious heart disease such as severe heartfailure

7. Active malignant tumors or a history of malignant tumors within 5 years beforeinformed consent obtained

8. History of allergy to vitamin D

9. Any condition which in the opinion of the investigator unfit for the study