24-hour Urine Calcium Predicts Reduced Fracture Incidence and Improved BMD After Surgery for Primary Hyperparathyroidism.

CONTEXT: Contemporary patients with primary hyperparathyroidism are diagnosed with milder disease than previously. Clinical and biochemical factors predictors with impact on fracture incidence and bone mineral density after surgery have not been firmly established.

OBJECTIVE: To investigate predictors of fracture incidence and bone mineral density preoperatively and after surgery for primary hyperparathyroidism (pHPT).

DESIGN: Prospectively collected surgical cohort with matched population controls. Data were cross-linked with the Swedish National Patient Register, the Prescribed Drug Register, and the Cause of Death Register.

SETTING: Tertiary referral center.

PATIENTS OR OTHER PARTICIPANTS: 709 patients with successful parathyroidectomy for pHPT, and 2,112 controls matched on sex, age, and municipality were included in the study.

MAIN OUTCOME MEASURES: Fracture incidence, absolute change and ≥2.77% increase in bone mineral density of femoral neck, L2-L4 and distal third of radius at 1-year follow-up.

RESULTS: Patients with pHPT had an increased fracture incidence before surgery but not after pHPT surgery. Fracture incidence after surgery was inversely related to preoperative 24-hour urine calcium (IRR for the highest tertile 220- mg/d 0.29, CI 95% 0.11-0.73). Serum and 24-hour urine calcium, parathyroid hormone, osteocalcin and adenoma weight were all associated with bone mineral density recovery after surgery.

CONCLUSIONS: 24-hour urine calcium is the most important biochemical variable to predict a decreased fracture incidence and improved bone mineral density after surgery for pHPT.