Skeletal calcium homeostasis and countermeasures to prevent disuse osteoporosis

摘要: Maintenance of a skeleton capable resisting the stresses everyday life is dependent on mechanical forces applied to during normal activity in 1-G environment. When effects longitudinal are removed, as with space travel or inactivity, bone and mineral lost because resorption greater than formation. Ninety healthy young men were studied 5-36 weeks continuous bed rest. During urinary calcium increases rapidly by sixth week rest, output has risen 100 mg/day, plateaus for several weeks, then decreases but remains above ambulatory baseline thereafter. This occurred even though they received vitamin D supplements throughout study. Calcium balance becomes negative after 2 end first month, 200 mg/day lost. The loss continues at this rate least 36 weeks. Calcaneal loses 5% its mass each month. Attempts prevent disuse osteoporosis both biochemical means, including exercise, skeletal compression, increased hydrostatic pressure lower body, supplemental and/or phosphorus, calcitonin, etidronate not successful.