[Secondary osteoporosis UPDATE. Bone loss due to bed rest and human space flight study].

Bone loss and renal stone are significant medical concerns for bed rest subjects and space flight astronauts. Bone mineral loss occurs as secondary osteoporosis due to the unloading of weight bearing bones during bed rest and space flight. Increased bone resorption and bone metabolic uncoupling promote bone loss through the release of calcium from unloaded weight bearing bones. The rate of bone mineral loss during bed rest and space flight is about 1-2 percent per month, and recovery requires a period three or four times longer. To prevent bone loss caused by bed rest and space flight, a prophylactic countermeasure program based on scientific evidence should be developed.