“Age-related osteoporosis is characterized by reduced bone formation and accumulation of fat in the bone marrow compartment.
Here, we report that the type 1 cannabinoid receptor (CB1) regulates this process…
The CB1 receptor is therefore unique in that it regulates peak bone mass through an effect on osteoclast activity, but protects against age-related bone loss by regulating adipocyte and osteoblast differentiation of bone marrow stromal cells.”
http://www.ncbi.nlm.nih.gov/pubmed/19656492
“Cannabis may prevent osteoporosis” http://news.bbc.co.uk/2/hi/uk_news/scotland/edinburgh_and_east/8199007.stm