What happens to the bone structure after normocalcemic primary hyperparathyroidism surgery?

Bone disease in primary hyperparathyroidism is a clear indication for surgical treatment. However, it is not known whether surgery benefits hypercalcemic primary hyperparathyroidism and normocalcemic primary hyperparathyroidism equally. The aim of our study was to evaluate the bone changes in patients undergoing parathyroidectomy based on the biochemical profile 1 and 2 years after surgery.

This prospective study included 87 consecutive patients diagnosed with primary hyperparathyroidism who underwent surgery between 2016 and 2018. Bone densitometry (1/3 distal radius, lumbar, and femur) and bone remodeling markers (osteocalcin, type 1 procollagen [P1NP], β-cross-linked telopeptide of type I collagen [BCTX]) were performed preoperatively and postoperatively. Postoperative changes in bone mineral density and bone markers were compared and evaluated according to the clinical characteristics and the individual biochemical profile.

One year after surgery, all patients showed an increase in bone mineral density at the lumbar site (mean, 0.029 g/cm²; range, 0.017-0.04; P < .001) and femur neck (mean, 0.025 g/cm²; range, 0.002-0.05; P < .001); however, there were no changes in the distal third of the radius (mean, -0.003 g/cm²; range, -0.008 to 0.002; P = NS). There were no significant differences when comparing normocalcemic primary hyperparathyroidism and hypercalcemic primary hyperparathyroidism. Serum osteocalcin (37 ± 17.41), P1NP (67.53 ± 31.81) and BCTX (0.64 ± 0.37) levels were elevated before surgery. One year after the surgery, we observed a significant decrease in P1NP (33.05 ± 13.16, P = .001), osteocalcin (15.80 ± 6.19, P = .001), and BCTX (0.26 ± 0.32, P < .001) levels.

Our findings indicate that parathyroidectomy has similar benefits for normocalcemic primary hyperparathyroidism and hypercalcemic primary hyperparathyroidism in terms of bone improvement. Although the most substantial improvement occurred during the first postoperative year in both groups, we consider that studies with longer follow-up are warranted.