A Safety, Tolerability and Pharmacodynamics Study of ACE-011 (ActRIIA-IgG1) in Healthy Postmenopausal Women

Inclusion Criteria: 1. Subject is a postmenopausal woman, 45-85 years old (inclusive). 2. Subject has had 12 months of spontaneous amenorrhea, OR 6 months of spontaneous amenorrhea with serum follicle stimulating hormone (FSH) levels \>40 IU/L OR is 6 weeks postsurgical bilateral oophorectomy with or without hysterectomy. 3. Subject is taking at least 500 mg of calcium supplement and 400 IU of vitamin D daily and has been following this regimen for at least 4 weeks prior to the first dose of study drug administration. 4. Subject has a body mass index (BMI) of ≥ 18.5 to \< 30. 5. Subject must give written informed consent. If required by local law, candidates must also authorize the release and use of protected health information (PHI). Exclusion Criteria: 1. Subject has a history of clinically significant major disease (as determined by the Investigator). 2. Subject has a history of hyperparathyroidism, hypoparathyroidism, hypocalcemia, rheumatoid arthritis, myeloproliferative disorder, gout, Paget's disease of the bone, or osteomalacia. 3. Subject has had a long bone fracture within the past 6 months prior to enrollment, or an osteoporosis-related fracture within the previous 2 years. 4. Subject has a history of opportunistic infection, or has had a serious local or systemic infection within 3 months prior to screening. 5. Subject has a history of severe allergic or anaphylactic reactions. 6. Subject had major surgery within the previous 3 months. 7. Subject has a history of drug or alcohol abuse, or tests positive in a drug and alcohol screen at screening or on Day 1 prior to dosing. 8. Subject consumed any alcohol within 72 hours prior to dosing. 9. Subject gave a blood donation (one unit or more) within 1 month prior to dosing, or plans to give a blood donation during the course of the study. 10. Subject has taken any of the following bone active medications: * Teriparatide at any time in their lifetime. * Fluoride therapy for more than 3 months during the previous 2 years. * Estrogen, androgen, anabolic steroids, corticosteroids (excluding inhaled, topical or local injections for joint pain), calcitonin, or other bone active drugs (e.g. selective estrogen receptor modulators) within the 4 months prior to screening. Bisphosphonates: * If treated for more than 6 months at any time in their lifetime. * If treated for 3 to 6 months within 2 years of screening. * If treated for less than 3 months within 6 months of screening. 11. Subjects with chronic stable diseases including migraines, hypertension, hyperthyroid disorder, hypothyroid disorder, gastroesophageal reflux disease, or mild depression/anxiety will be excluded unless the investigator does not have safety or compliance concerns at study entry.