Fracture risk in primary hyperparathyroidism

A key component in the decision to perform surgery on patients with primary hyperparathyroidism (HPT) is their skeletal status. Consequently, fracture risk in these patients has been investigated in a number of observational studies. Our group reported on a population-based cohort of residents from Rochester, MN, with primary HPT recognized during a 28-year period (1965-1992). The majority of these patients were asymptomatic, and most (77%) were managed conservatively. By contrast, a recent Danish study reported on a cohort of 674 patients, all of whom had surgery for primary HPT. Nonetheless, the risk of fracture was increased remarkably similarly in the two populations: vertebrae, approximately 3-fold; forearm, approximately 2-fold; hip, approximately 1.5-fold; and all fractures, approximately 1.5-fold. In both studies, parathyroid surgery seemed to have a protective effect. These (and previous studies) indicate that overall fracture risk is increased in primary HPT patients. An increase in forearm fracture risk is a relatively uniform finding and is consistent with known effects of parathyroid hormone (PTH) on cortical bone. However, the increase in vertebral fracture risk seen in most (but not all) studies does not fit with the observation that cancellous bone mass/structure is preserved in primary HPT patients. Based on these findings, future directions for research include (1) rigorously testing, in prospective studies, whether vertebral fracture risk is, in fact, increased in this disorder, and if so, determining the possible biomechanical mechanism(s) for this increase; and (2) testing whether the trend to increased hip fracture risk seen in some studies is real and whether it is more closely linked to cervical or intertrochanteric fractures.