Biochemical effects of a calcium supplement in osteoporotic postmenopausal women with normal absorption and malabsorption of calcium.

Although calcium supplements are widely used to reduce bone resorption in osteoporosis, their beneficial effect is not conclusively established. We have studied the acute (after 12 h) effects of an oral calcium load (1 g) in a group of 35 osteoporotic postmenopausal women, comprising 19 subjects with normal absorption and 16 subjects with malabsorption of calcium. In the subjects with normal calcium absorption the fasting urinary total hydroxyproline/creatinine ratio fell from 0.021 to 0.017 (p less than 0.001), but in those with malabsorption of calcium it did not change significantly. This difference between the two groups was significant (p less than 0.01). These results indicate that an oral calcium load rapidly suppresses bone resorption in osteoporotic subjects with normal absorption of calcium, but not in those with malabsorption of calcium.