[Calcium and magnesium metabolism in the aged]

Although serum calcium concentration remains constant during ageing, the plasma concentration of calcium regulating hormones has been known to show dramatic change with ageing. The plasma concentration of parathyroid hormone increases with ageing, whereas plasma concentrations of calcitonin and active vitamin D metabolite decrease with ageing. The age-related change in plasma concentrations of calcium regulating hormones might be a major cause of the age-related bone loss by stimulating bone resorption and thereby releasing calcium from bone. On the other hand, the incidence of soft tissue calcification is known to increase with ageing. In order to further study the relationship between these age-related phenomena, we studied the relationship between radial bone mineral density (BMC) and aortic pulse wave velocity (PWV) which is considered to be a clinical index for the magnitude of aortic calcification. Multi-variate analysis showed the significant relationship (p less than 0.05) between BMC and PWV, suggesting that the decrease in bone mass might be an independent risk factor for the development of aortic calcification. Low calcium intake is an important factor for the development of age-related bone loss. The recommended dietary allowance (RDA) of calcium intake for the Japanese is considered to be 600 mg/day. In order to reevaluate RDA of calcium for the elderly Japanese women, a calcium balance study was performed in 13 subjects; six with osteoporosis (age: 75 +/- 2) and seven without osteoporosis (age: 72 +/- 2). Calcium balance in the individual subject was evaluated by measuring the intake of calcium (food) and output (feces and urine) every 2 days.(ABSTRACT TRUNCATED AT 250 WORDS)