[Is there a role for a random measurement of 24-hour urine calcium excretion and serum total alkaline phosphatase in the determination of fracture risk in osteoporotic postmenopausal women?].

UNLABELLED: Our objective was to explore whether a casual determination of 24-hour urinary calcium excretion and serum total alkaline phosphatase (TAP), in osteoporotic postmenopausal women are independent predictors for osteoporotic fracture. Subjects were 121 women with postmenopausal osteoporosis (mean age 62.8 +/- 9.9) segregated in two study groups based on prevalence of osteoporotic fractures (51 women with prevalent fractures and 70 without fractures), similar in terms of age and BMI. We measured bone mineral density (BMD) by DXA at lumbar spine and femoral neck. Vertebral fracture assessment was done by plain X ray evaluation. Routine blood tests and extensive endocrine evaluation were performed in all patients to exclude secondary causes of osteoporosis. Serum TAP, calcium, phosphate and urinary calcium excretion was measured to evaluate bone metabolism. We did not find any significant differences between groups regarding lumbar T score (-3.1/-2.9 SD), femoral neck T score (-2.2/-1.8 SD), lumbar Z score (-1.5/-1.9 SD) or femoral neck Z score (-1.5/-1.8 SD). Serum TAP was higher in fracture group (211.5 UI) comparing to non-fracture osteoporotic women (208.3 UI) without statistical significance. We were not able to find any significant difference between groups in terms of urinary calcium excretion (9.13/5.4 mEq/24h) or serum total calcium (4.8/4.9 mmol/l).

CONCLUSION

in spite of a mean TAP near the upper limit of normal range which could be related to low bone mass, there is no significant relationship to fracture risk in osteoporotic postmenopausal women. Based on our data, a casual measurement of urinary calcium excretion seems irrelevant for BMD independent fracture risk assessment in this clinical setup.