Osteoporosis in Spaceflight

No major medical diffifulties were experienced during spaceflight in the era of Russian Vostok/ Voshot or spaceflight programs of Mercury and Gemini, however, when prolonged stays in space stations began in the 1980’s, astronauts or Russian cosmonauts had an increased risk of suffering from renal stones, and resultant bone loss. The detailed mechanism behind this phenomenon is still unknown, but one explanation is that unloading of the skeleton that would normally bear the bodyweight led to calcium (Ca) leaving the bones for the bloodstream. The Ca entered the kidneys, filtered into the urine, causing hypercalciuria, and increased the risk of kidney stone formation. Such stones formed in the kidney break down and travel into the ureter, causing flank pain. Thus astronauts continually subjected to risks of bone and Ca loss while in microgravity [Buckey, 2006].