Endocannabinoids are marijuana-like chemicals produced naturally in humans and animals that bind to the same receptors as do plant-derived cannabinoids such as THC.

Researchers at the Bone Laboratory of the Hebrew University in Jerusalem found a high number of cannabis receptors present in the bones of mice. Mice that lacked these receptors developed severe osteoporosis as they aged. Researchers reported that the administration of the synthetic cannabinoid HU-308 slowed the development of osteoporosis, stimulated bone building and reduced bone loss. "These results demonstrate that the endocannabinoid system is essential for the maintenance of normal bone mass, . [and that the cannabinoid receptor] offers a molecular target for the diagnosis and treatment of osteoporosis," researchers concluded.

Osteoporosis is a degenerative skeletal disease characterized by a deterioration of bone tissue.
Patients with osteoporosis are at risk for suffering multiple fractures and other serious
disabilities. Previous research on endocannabinoids and the endocannabinoid receptor system
indicates that cannabinoids may play a role in maintaining homeostasis (metabolic equilibrium) in
humans and other living organisms. Biological functions regulated by endocannabinoids include
appetite, body temperature, blood pressure, reproductive activity, learning capacity, and motor
coordination.

Full text of the study, "Peripheral cannabinoid receptor, CB2, regulates bone mass," is available in the January 10, 2006 edition of the Proceedings of the National Academy of Sciences of the USA. Abstracts of the study are available online at:

http://www.pnas.org/cgi/doi/10.1073/pnas.0504187103