Effect of calcium supplementation on urinary hydroxyproline in osteoporotic postmenopausal women.

Although calcium supplements are widely used to reduce bone resorption in osteoporosis, their beneficial effect is not conclusively established. We studied the effect of a calcium supplement (1 g/day for 8 days) in 14 postmenopausal osteoporotic women. The fasting urinary hydroxyproline/creatinine ratio decreased from 0.022 +/- 0.001 to 0.017 +/- 0.001 (p less than 0.005) indicating a significant reduction in bone resorption. Both the tubular maximum for phosphate reabsorption (1.12 +/- 0.06 to 1.34 +/- 0.07, p less than 0.005) and plasma phosphate concentration (1.04 +/- 0.04 to 1.14 +/- 0.04, p less than 0.01) increased, consistent with suppression of parathyroid hormone activity. These results support the concept that calcium supplementation is useful in the treatment of postmenopausal osteoporosis.