Prediction of bone mass change after parathyroidectomy in patients with primary hyperparathyroidism

A major challenge in the management of primary hyperparathyroidism (pHPT) i s the decision regarding which patients should undergo parathyroidectomy (P TX), although the Consensus Development Conference of the NIH has proposed guidelines for the indication of surgery. In the present study, changes in bone mineral density (BMD) after PTX were compared between pHPT patients wh o did and did not meet the NIH criteria, and we further tried to predict th e BMD change after PTX from preoperative parameters. The subjects were 44 p HPT patients (30 women and 14 men) who had had successful PTX. Lumbar and r adial BMD were measured before and 1 yr after PTX by dual energy x-ray abso rptiometry and single photon absorptiometry, respectively. Average annual p ercent increases in lumbar and radial BMD after PTX were 12.2 +/- 1.4% and 11.6 +/- 1.6% (mean +/- SEM), respectively, and those net increases were 0. 0803 +/- 0.0008 and 0.0484 +/- 0.0006 g/cm(2), respectively. There were no significant differences in percent or net changes in either radial or lumba r BMD after PTX between the groups divided according to each of the NIH cri teria, such as age (greater than or equal to 50 and <50 yr), serum calcium level (greater than or equal to 12 and <12 mg/dL) or the existence of urina ry stones (presence and absence). On the other hand, when the subjects were divided on the basis of radial BMD (above and below a z-score of -2), the annual percent and net increases in lumbar BMD and percent increase in radi al BMD after PTX were significantly higher in the group with the lower z-sc ore. Next, patients were divided into two groups with and without the indic ation of PTX based on NIH guidelines. Twenty-nine patients had the surgical indication by meeting one or more of these criteria and 15 patients had no indication without meeting any of the criteria. There were no significant differences between the two groups in annual percent or net changes in radi al or lumbar BMD after PTX. A stepwise multiple regression analysis reveale d that serum alkaline phosphatase level and the severity of cortical bone m ass reduction were the best predictors of both percentage and net changes i n lumbar BMD, with high determination coefficients (r(2) > 0.7). In conclus ion, a considerable increase in BMD could be obtained after PTX even in pat ients without surgical indication from the NIH. Alkaline phosphatase and th e severity of cortical bone mass reduction are clinically useful for predic ting the changes in lumbar BMD after PTX. The present findings provide a us eful clue for the indication of surgery in pHPT.