Endocrine Abstracts

Background: Osteoporosis is common in primary hyperparathyroidism (PHPT). It is also an indication for parathyroidectomy in PHPT. Bone mineral density (BMD) measured by dual-energy x-ray absorptiometry (DXA) increases after successful surgery. Alendronate significantly increases BMD in PHPT patients not undergoing surgery. It is not known whether surgery alone or in combination with postoperative zoledronic acid more efficiently improves bone health in PHPT.

Objective: To compare the effects of surgery alone with surgery in combination with zoledronic acid on bone turnover and BMD in PHPT.

Methods: Randomized, double-blind, placebo-controlled study of PHPT patients with osteoporosis including DXA and bone marker measurements at baseline, 1- and 2-year follow-up.

Patients: 1–3 months after parathyroidectomy, 56 patients with PHPT were randomized to zoledronic acid (ZOL; f/m (25/3), mean age 67.9 yrs) or placebo (PBO; f/m (22/6), mean age 69.0 yrs).

Results: BMD significantly improves 2 yrs after parathyroidectomy, with significantly better scores at the femoral neck (FN) and lumbar spine (LS) in the ZOL compared to the PBO group (Z-score in FN; P = 0.045 and T- and Z-scores in LS; P = 0.039 and 0.017, respectively). Bone turnover markers (P1NP, CTX, ALP) decrease significantly more in the ZOL compared to the PBO group (P <0.001 for all markers). Of the 18 patients who before surgery had received bisphosphonates for >1 yr, BMD improved significantly in the femoral neck and lumbar spine in the ZOL (n = 10; P < 0.001–0.01 for all) but only in the lumbar spine in the PBO (n = 8, P = 0.03) group.

Conclusion: BMD increases after parathyroidectomy both with and without zoledronic acid. However, BMD improves significantly more when combined with postoperative zoledronic acid.