CALCIOTROPIC HORMONES AND MARKERS OF BONE REMODELING IN AGE-RELATED (TYPE-II) FEMORAL-NECK OSTEOPOROSIS - ALTERATIONS CONSISTENT WITH SECONDARY HYPERPARATHYROIDISM-INDUCED BONE-RESORPTION

Background. Both a decrease in bone formation and the skeletal consequ ences of secondary hyperparathyroidism have been implied in the pathog enesis of age-related femoral neck osteoporosis. However, studies usin g biochemical indices of bone remodeling in hip fracture patients have yielded conflicting results. Similarly, secondary hyperparathyroidism has not been a consistent Ending in this population. Some of these in consistencies might reflect differences in the assays used as well as in the timing of the sampling. Moreover, measurements were mostly perf ormed in a limited number of patients. In this regard, the aim of the present study was to analyze potential alterations in bone metabolism in a large population of elderly hip fracture patients. Methods. Circu lating concentrations of 25-hydroxyvitamin D [25(OH)D], 1,25-dihydroxy vitamin D [1,25(OH)(2)D-3], intact parathyroid hormone (PTH), and calc itonin were measured in 117 elderly women (within a few hours after su staining a fracture of the proximal femur) and in 117 healthy age-matc hed controls. In addition, serum osteocalcin and urinary excretion of (deoxy)pyridinoline were determined as markers of bone formation and r esorption, respectively. Results. Serum levels of 25(OH)D and 1,25(OH) (2)D-3 were decreased in hip fracture patients. When correcting for di fferences in serum vitamin D binding protein, serum 25(OH)D was still significantly lower in patients than in controls, whereas serum 1,25(O K)(2)D-3 was not. Moreover, 25(OH)D deficiency in hip fracture patient s was associated with an increase in circulating PTH and urinary excre tion of (deoxy)pyridinoline. Serum osteocalcin, on the other hand, was significantly decreased in fracture patients. There: was net statisti cally significant difference in calcitonin. Conclusion. These data sug gest that there is reduced bone formation and increased bone resorptio n in patients with hip fracture, Although limited by its cross-section al design, the present study emphasizes the role of secondary hyperpar athyroidism-induced bone resorption in the pathogenesis of age-related osteoporosis, mainly due to a lack of 25(OH)D.