BONE-DISEASE IN CALCIUM STONE FORMING PATIENTS

The association between idiopathic hypercalciuria and osteopenia (OF) has been recently recognized. It is not established whether or not cal cium intake plays a critical role in the loss of bone mass. Fifty-five calcium stone forming patients with either absorptive hypercalciuria (AH) or fasting hypercalciuria (FH), 29 males and 26 premenopausal fem ales, were submitted to dual photon absorptiometry at lumbar spine. Ca lcium intake was assessed by a 72 hr dietary record. OP was detected i n 20% (11/55) of patients, being more common among men, 9/26 (35%) tha n in women, 2/29 (7%), p < 0.05. Male FH patients presented lower mean bone mineral density (BMD) than sex, weight and age-matched control(1 .058 +/- 0.18 vs 1.209 +/- 0.13 g/cm(2), X +/- SD, p < 0.05). OP was m ore frequent in FH patients, 7/20 (35%) than in AH patients 4/35 (11%) , albeit the difference was not statistically significant. There was n o correlation between calcium intake and BMD measurement. Six osteopen ic male FH patients were further submitted to histomorphometric evalua tion with tetracycline double labeling. Bone volume was lower than the controls (13.2 +/- 3.0 vs 27.2 +/- 3.7%, p < 0.05). Osteoid surfaces were reduced, although not significantly (10.1 +/- 8.2% vs 15.9 +/- 6. 7%). Eroded surfaces were markedly increased (23.9 +/- 13.4 vs 4.2 +/- 1.4%, p < 0.05). The bone formation rate was very low with a complete lack of tetracycline double labeling in 4 patients. These data sugges t low bone volume, tendency to low bone formation, increased bone reso rption and a severe mineralization defect, consistent with normal or l ow bone turnover osteoporosis.