Bone involvement in idiopathic hypercalciuria.

Background: To evaluate bone involvement in idiopathic hypercalciuria, 40 lithiasic patients and 10 controls were studied. Methods: According to urinary calcium excretion, patients were first classified as hypercalciuric (H ca , n = 22) and normocalciuric (N ca , n = 18). The H ca patients were then subclassified according to bone densitometry (BMD) as osteopenic (H ca O, n = 10) and non-osteopenic (H ca NO, n = 12). Routine biochemistry, dietary records, bone histomorphometry, and cytokines (IL-1β. IL-6, and TNF) production by peripheral blood mononuclear cell cultures were studied. Results: There were no differences in routine biochemistry between H ca and N ca groups, except for urinary calcium. Inadequate nutrition was observed in H ca group, showing high protein (80.9% of the patients), carbohydrate (76.2%) and sodium (90%) intake. Calcium intake was low in H ca (57%) and N ca (83%) groups. IL-6 and TNF were not different between the H ca and N ca groups. IL-1β levels were significantly high in both groups when compared to controls. IL-6 and TNF were higher in H ca O than N ca . BMD in femoral neck in H ca O was lower than in H ca NO and N ca groups. Eroded surface (ES/BS) increased in 91% of the H ca group and 36% had a mineralization defect. In the H ca O group serum PTH correlated negatively with trabecular bone volume (BV/TV) and positively with ES/BS. 1,25(OH) 2 D 3 levels correlated positively with osteoblastic surface. Calcium intake correlated positively with BV/TV and inversely with ES/BS. A negative correlation was observed between IL-6 levels and Z score of the femoral neck. Conclusion: Bone involvement was detected in a young population with nephrolithiasis demonstrating that a strict follow-up is necessary in order to control hypercalciuria.