Skeletal effects of combined medical and surgical management of primary hyperparathyroidism.

BACKGROUND

Parathyroidectomy (PTX) increases bone mineral density and decreases fracture risk in patients with primary hyperparathyroidism. This study examined the effect of adding bisphosphonates either before or after PTX on skeletal outcomes.

METHODS

A retrospective cohort study of bisphosphonate-naïve patients (1995-2016) with osteoporosis and primary hyperparathyroidism (calcium >10.5 mg/dL; PTH >65) was performed. Time-varying Cox regression was used to estimate an adjusted risk of any fracture in 5 comparison groups: observation, bisphosphonates alone, PTX alone, bisphosphonates then PTX, and PTX then bisphosphonates. The secondary outcome was change in bone mineral density of the hip.

RESULTS

The cohort comprised 1,737 patients, of whom 303 underwent PTX (17%), 433 received bisphosphonates only (25%), 125 had bisphosphonates then PTX (7%), and 69 had PTX then bisphosphonates (4%). PTX was associated with a decrease in fracture risk (HR 0.55, 95% CI 0.35-0.84), as was bisphosphonates then PTX (HR 0.46, 95% CI 0.25-0.83). In contrast, the fracture risks associated with PTX then bisphosphonates (HR 1.09, 95% CI 0.65-1.81) and bisphosphonates alone (HR 0.82, 95% CI 0.62-1.08) were similar to observation. Hip bone mineral density increased after both PTX (5.50%, 95% CI 3.39-7.61) and PTX then bisphosphonates (6.30%, 95% CI 2.53-10.07).

CONCLUSION

Bisphosphonate initiation after PTX may interfere with the beneficial effects of PTX on fracture risk in osteoporotic patients with primary hyperparathyroidism.