A Study to Evaluate the Effect of Romosozumab (AMG 785) on Bone Quality of the Forearm in Postmenopausal Women with Low Bone Mass

- Healthy females between 55 to 80 years of age - Postmenopausal females (based on medical history) defined as 12 continuous months of spontaneous amenorrhea -- Women 60 years of age and older will be considered postmenopausal -- Women 55-59 must have a serum follicle-stimulating hormone result > 40 mIU/mL and serum estradiol ≤ 20 pg/mL - Low bone mineral density (BMD), defined as a BMD T-score between -1.0 and -2.5 at the lumbar spine (L1-L4) and/or femoral neck - Weight ≤ 98 kg (216 lb) and/or height ≤ 196 cm (77 in) - 25-hydroxyvitamin D ≥ 20 ng/mL at screening - Willing and able to take ≥ 500 mg calcium and ≥ 400 IU (but ≤ 1,000 IU) vitamin D daily

- Osteoporosis, defined as a BMD T-score ≤ -2.5 at the lumbar spine or femoral neck - History of vertebral fracture, or fragility fracture of the wrist, humerus, hip or pelvis - Diagnosed with any condition that will affect bone metabolism - Subjects with fewer than 2 evaluable vertebrae; metal in forearms bilaterally that would not allow for at least one evaluable forearm - Administration of the following medications within 6 months before study drug administration. This includes all routes of administration, for example intranasal and topical skin patches, unless otherwise noted: -- Hormone replacement therapy [(eg, estrogen, estrogen-like compounds such as raloxifene). Infrequent use of estrogen vaginal creams (< 3 times per week) is allowed.] -- Calcitonin -- Parathyroid hormone (or any derivative) -- Glucocorticosteroids (inhaled or topical corticosteroids administered more than 2 weeks before the enrollment date are allowed) -- Anabolic steroids -- Calcitriol, and available analogues - Administration of daily, weekly, or monthly bisphosphonates (BP) unless meeting the following criteria: -- < 2 weeks of BP use requires a 2-month washout period -- 2 weeks to 3 months of BP use requires a 9-month washout period -- 3 to 6 months of BP use requires a 1-year washout period -- > 6 months of BP use requires a 3-year washout period; - Greatly differing levels of physical activity or constant levels of intense physical exercise during the 6 months before study drug administration - Known sensitivity to mammalian-derived drug preparations - Known to be hepatitis B surface antigen, hepatitis C virus or human Immunodeficiency virus (HIV) positive or a known diagnosis of acquired immunodeficiency syndrome (AIDS) - Any organic or psychiatric disorder, which, in the opinion of the investigator, poses a risk to subject safety and may prevent the subject from completing the study or interfere with the interpretation of the study results - Unavailable for follow-up assessment or any concerns for subject’s compliance with the protocol procedures - Any other condition that might reduce the chance of obtaining data required by the protocol or that might compromise the ability to give truly informed consent - History or evidence of a clinically significant disorder, condition or disease that, in the opinion of the Investigator or Amgen physician would pose a risk to subject safety or interfere with the study evaluation, procedures or completion - Clinically significant abnormality during the screening physical examination, electrocardiogram (ECG) or laboratory evaluation - Participation in another clinical study within 4 weeks of screening or within 5 times the half-life of the investigational agent in the other clinical study, if known - Has donated or lost 400 mL or more of blood or plasma within 8 weeks of study drug administration - Previous AMG 785 exposure