Study Purpose: This study is testing a drug called AGA2118 for postmenopausal women with low bone mass. Low bone mass means the bones are weaker and more likely to break. A placebo is a substance with no medicine in it, used to compare with the real medicine.

Study Details: The study lasts for 2 years. In the first year, women will receive either AGA2118 or a placebo. Neither the participants nor the researchers know who gets which, making it a "double-blind" study to ensure fairness. After the first year, women will either keep taking the same medicine, switch to a different one, or stop taking it but stay in the study for observation until the second year ends.

• Participation: 2 years total (1 year treatment + 1 year follow-up).
• Eligibility: Women aged 55-80 without serious health problems related to bones or certain other conditions.
• Benefits/Risks: Learn about AGA2118's effect on bones, but potential risks exist as with any study.