The skeleton should be thought of as a dynamic, metabolically active, and functionally diverse organ. In addition to providing the levers for muscle and locomotion, bone supports and protects vital organs and is the site of hematopoiesis in the marrow. Metabolically, bone is central in calcium and phosphate homeostasis, and acid–base balance via buffering hydrogen ions. Recent studies suggest that bone may have additional important endocrine roles in fertility, glucose metabolism, appetite regulation and muscle function.