Histomorphometric analysis of bone in idiopathic hypercalciuria before and after treatment with thiazide

Twenty-seven normocalcemic patients aged 11-69 yrs with recurrent renal stone formation and idiopathic hypercalciuria were studied before and after treatment with hydrochlorthiazide (TD) 50 mg twice a day for 6 months. Hypercalciuria was defined as a 24 h renal calcium excretion of more than 7.5 mmol for males and 6.3 mmol for females. Quantitative histomorphometric analysis of iliac crest bone biopsies were performed before and after treatment. TD treatment increased the adjusted serum calcium level (p less than 0.01), whereas no significant effects on the serum levels of phosphorous, alkaline phosphatase or iPTH were found. The urinary calcium/creatinine ratio decreased (p less than 0.01) during TD treatment, whereas no change in the urinary phosphorous/creatinine ratio was found. The histomorphometric analysis revealed a reduction in the extent of eroded surfaces (p less than 0.05) and bone formation rate (p less than 0.05) as well as a decrease in the osteoid thickness (p less than 0.05) during TD treatment. No effect on the trabecular bone volume was found. A reduction in the activation frequency of new remodeling sites and thereby a reduced bone turnover during TD treatment can explain the observed histomorphometric changes. The decrease in osteoid thickness may be related to the increased serum calcium concentration leading to better conditions for mineralization.