Mechanisms of Anabolic Osteoporosis Therapy

Inclusion Criteria:

All postmenopausal women who are prescribed romosozumab by their treating physicians, meet the FDA-defined indication for romosozumab, and who are not at increased risk for a bone marrow aspirate or bone biopsy will be offered enrollment. The FDA approved indication for romosozumab is: "the treatment of osteoporosis in postmenopausal women at high risk for fracture, defined as a history of osteoporotic fracture, or multiple risk factors for fracture; or patients who have failed or are intolerant to other available osteoporosis therapy." Volunteers must be:

1. Female aged \> 45 years
2. Postmenopausal by either of the following criteria:

   1. \> 36 since last spontaneous menses
   2. \> 36 months since hysterectomy, plus serum FSH \> 40 units / liter if \< 60 years

Exclusion Criteria:

* renal disease (stage 4 CKD)
* elevated blood PTH (intact PTH \> 77 pg/ml).
* serum 25-OH vitamin D \< 20 ng/ml
* 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 would preclude the subject from providing adequate informed consent or completing the protocol procedures.
* known congenital or acquired bone disease other than osteoporosis.
* exposure to oral bisphosphonates within the past 3 months, denosumab in the last 12 months, intravenous bisphosphonates within the past 24 months.
* exposure to estrogens, SERMs, or calcitonin, oral or parenteral glucocorticoids for more than 14 days in the past 2 months.
* any prior exposure to romosozumab.