Prediction of changes in bone density after operation for primary hyperparathyroidism

Primary hyperparathyroidism (pHPT) is associated with osteopenia. However, the individual variation in recovery in bone mass after surgery is large. Therefore, modes of prediction of the increase in bone mass after parathyroid surgery were investigated. Preoperatively and at one year after surgery bone mineral content (BMC) in the distal radius was measured with single photon absorptiometry technique in 40 patients with pHPT. Serum levels of calcium, intact parathyroid hormone (PTH), alkaline phosphatase, osteocalcin and Vitamin D metabolites were also determined. Preoperatively, Z-score of BMC was -0.85 +/- 1.20 SD below the normal mean. There was a modest association between BMC and serum levels of osteocalcin (r = -0.34; P < 0.05), and dihydroxycholecalciferol (r = -0.35; P < 0.05). At one year after surgery, mean BMC increased by 2% (P < 0.05), but with a wide dispersion. Preoperative Z-score of BMC correlated with the relative change in BMC (r = -0.33; P < 0.05). An increase in BMC with 95% confidence was evident in 10 of the patients. None of these patients had a preoperative Z-score of BMC above the mean expected for age and sex. We conclude that the increase in bone mass after surgery for pHPT is small and evident only in a portion (approximately 25%) of patients. Hence, a decrease in bone mass should not be a major indication for surgery in pHPT.