Reduced bone mass in children with idiopathic hypercalciuria and in their asymptomatic mothers

Background. Patients with nephrolithiasis and idiopathic hypercalciuria (IH) may exhibit reduced bone mineral density (BMD). Most studies measuring BMD in IH patients employing dual-energy X-ray absorptiometry (DEXA) have been performed in adults, and no study has been conducted in North-American children. Optimal bone mineral accretion during childhood and adolescence is critical to the attainment of a healthy adult skeleton. Bone mineral accretion and eventual adult peak bone mass are largely dependent on genetic factors. Hypercalciuria is also frequently linked to genetic determinants. Therefore, we carried out a cross-sectional evaluation of bone mineral metabolism in children with IH, and in their asymptomatic premenopausal mothers. Methods. Quantitative BMD using DEXA was performed in 21 children with IH and in their asymptomatic mothers. Bone resorption was assessed by measuring the urinary concentrations of pyridinoline and deoxypiridinoline. Simultaneous calcium-modulating hormonal determinations, including serum intact immunoreactive parathyroid hormone and 1,25(OH)(2)D-3, were performed. The expression of interleukin-1alpha (IL-1alpha) by peripheral blood mononuclear cells (PBMCs) was determined by polymerase chain reaction. Results. Reduced BMD values were observed in eight children (38%) and in seven mothers (33%). The children of osteopenic mothers exhibited significantly reduced BMD Z-score values of lumbar spine (P < 0.05) when compared with children of mothers with normal BMD. Bone resorption markers were normal in most children with IH. Hypercalciuria was detected in five out of 20 (25%) asymptomatic mothers and it correlated (r = -0.81) to femoral BMD in mothers with osteopenia. The expression of IL-1alpha mRNA by PBMCs from IH children did not differ from controls. Conclusions. Reduced BMD was detected in a large proportion of children with IH. Hypercalciuria and reduced BMD were uncovered in a substantial number of their otherwise healthy asymptomatic mothers. The diminished BMD in adults with IH may start early in life, could be influenced by genetic factors, and may represent a risk factor for osteoporosis later in life.