Familial hypocalciuric hypercalcaemia. III: Bone mineral metabolism.

Bone mineral metabolism was studied in 10 subjects with familial hypocalciuric hypercalcaemia (FHH) and 10 age-, sex- and surface area matched healthy controls. Bone turnover was estimated by urinary calcium and hydroxyproline excretions relative to creatinine (Ca/Creat and OHPr/Creat, respectively), serum bone Gla-protein (S-BGP) and serum alkaline phosphatase (S-ALP). Bone status was evaluated by measurement of bone mineral content (BMC) on both forearms and X-ray examinations of the hands. Ca/Creat and OHPr/Creat (indices of bone resorption) were both significantly higher in the FHH group than in the controls. S-BGP and S-ALP (indices of bone formation) tended towards a higher level in the FHH subjects, but the differences were not significant. The BMC values were similar in the two study groups and did not change with time. We conclude that these patients with FHH might have a bone turnover higher than normal, and that the increased bone resorption must be paralleled by an increased bone formation.