90% of protein in bone is type I collagen
Type I collagen is also the major structural protein in tendons and skin
Calcium in bone turns over 100% per year in infants
Calcium in bone turns over 18% per year in adults
Bone resorption by osteoclasts
--> New bone formation by osteoblasts
Cycle takes ~ 100days
Renewal rate for bone
4% per year for compact bones
20% per year for trabecular bones
PTH accelerates bone resorption
Oestrogen slows bone resorption
* Inhibition of cytokines (e.g. IL-1, IL-6, TNF-alpha) which stimulates osteoclasts
* Stimulates TGF-beta which increase apoptosis of osteoclasts