Objective and design: The prevalence and the effects of hypercalciuria on bone in patients with primary osteoporosis are poorly defined. We therefore retrospectively analyzed the data of 241 otherwise healthy women. They were 45-88 years of age and had been referred for their first visit to our Unit for Metabolic Bone Diseases over a 2-year period because of primary osteoporosis (bone density T-score < -2.5).
Methods: The main parameters of calcium and skeletal metabolism had been analyzed in all subjects. This population was then divided into two groups, according to the presence (HC+) or absence (HC-) of hypercalciuria.
Results: Elevated urinary calcium was present in 19% of the subjects. Due to the selection criteria, spinal and femoral bone loss was similar in the two groups. Urinary calcium, phosphate and fractional calcium excretion were higher in hypercalciuric patients. In a logistic regression model, the higher the Tm of phosphate, the lower the risk of hypercalciuria (odds ratio 0.33, confidence interval 0.18-0.62). On the contrary, hypercalciuria was the most important predictor of low bone mass in HC+ (accounting for more than 50% of the variance in spinal bone density).
Conclusions: Hypercalciuria is a common feature in postmenopausal bone loss. Since increased urinary calcium excretion and low bone mass appear to be linked, hypercalciuria seems to be an important determinant of reduced bone density in this setting as well.