Primary hyperparathyroidism and fracture probability

Abstract

The incidence of hip and major osteoporotic fracture was increased in patients with primary hyperparathyroidism even in patients not referred for parathyroidectomy. The risk of death was also increased which attenuated an effect on fracture probabilities. The findings argue for widening the indications for parathyroidectomy in mild primary hyperparathyroidism.

Introduction: Primary hyperparathyroidism (PHPT) is associated with an increase in the risk of fracture. In FRAX, the increase in risk is assumed to be mediated by low bone mineral density (BMD). However, the risk of death is also increased and its effect on fracture probability is not known.

Objective: The aim of this study was to determine whether PHPT affects hip fracture and major osteoporotic fracture risk independently of bone mineral density (BMD) and whether this and any increase in mortality affects the assessment of fracture probability.

Methods: A register-based survey of patients with PHPT and matched controls in Denmark were identified from hospital registers. The incidence of death, hip fracture, and major osteoporotic fracture were determined for computing fracture probabilities excluding time after parathyroidectomy. The gradient of risk for fracture for differences in BMD was determined in a subset of patients and in BMD controls. The severity of disease was based on serum calcium and parathyroid hormone levels.

Results: We identified 6884 patients with biochemically confirmed PHPT and 68,665 matched population controls. On follow-up, excluding time after parathyroidectomy in those undergoing surgery, patients with PHPT had a higher risk of death (+52%), hip fracture (+48%), and major osteoporotic fracture (+36%) than population controls. At any given age, average 10-year probabilities of fracture were higher in patients with PHPT than population controls. The gradient of fracture risk with differences in BMD was similar in cases and controls. Results were similar when confined to patients not undergoing parathyroidectomy. Fracture probability decreased with the severity of disease due to an increase in mortality rather than fracture risk.

Conclusion: The risk of hip and other major osteoporotic fracture is increased in PHPT irrespective of the disease severity. Fracture probability was attenuated due to the competing effect of mortality. The increased fracture risk in patients treated conservatively argues for widening the indications for parathyroidectomy in mild PHPT.

Keywords: Fracture probability; Hip fracture; Mortality; Primary hyperparathyroidism.