Factors affecting the distribution of zinc in the human skeleton

The zinc content of trabecular and cortical bone was measured in 28 femora obtained at autopsy. The ratios of calcium to zinc, phosphorus and magnesium were determined and their relation to age and vertebral density was investigated. The calcium/zinc ration was significantly higher in cortical as opposed to trabecular bone, whereas the calcium/phosphorus ratios were similar. There was a significant decrease in the calcium/zinc ratios of both trabecular and cortical bone with age and the former was directly related to vertebral density. The calcium/phosphorus ratios of trabecular and cortical bone did not vary significantly with age or vertebral density. Magnesium/zinc ratios tended to parallel the calcium/zinc ratios. The calcium/magnesium ratios were significantly higher in cortical as opposed to trabecular bone. None of these ratios appeared to be affected by the sex of the subject. These findings suggest that changes in skeletal zinc content with age are related to alterations in bone morphology, and that osteoporosis in man develops in association with zinc accumulation rather than zinc deficiency.