Effects of calcium deprivation and orchidectomy on bone composition in the rat

The effects of calcium deprivation and of orchidectomy, separately and combined, on body growth and bone composition have been examined in mature male rats. Calcium deprivation had no significant effect on the rate of body growth but femoral bone weight, bone ash weight and total calcium and phosphorus contents of the femora were reduced while the water content increased. However, there were no significant changes in the ratio of bone weight to body weight, in the amounts of calcium or phosphorus per unit weight of bone, or in the ratio of calcium to phosphorus in the bone. Orchidectomy reduced the rate of body growth, the mean weight of the femora and the ratio of bone weight to body weight. There was a 60% decrease in bone water and a 30--35% reduction in the calcium and phosphorus content of the femora but the amounts of ash, calcium and phosphorus per unit weight of bone fell by only 6--10%. The combination of orchidectomy and calcium deprivation had no greater effect on body weight, bone weight or bone composition than had orchidectomy alone. It is concluded that calcium deprivation and orchidectomy both cause osteoporosis in mature rats but the effects of orchidectomy are more severe than those of calcium deprivation and there appears to be some demineralization of the bone remaining after orchidectomy.