Bone mineral recovery after parathyroidectomy in patients with primary and renal hyperparathyroidism

Abstract

Patients with hyperparathyroidism (HPT) generally display reduced bone mass due to excessive PTH activity. The effect of parathyroidectomy on bone mass changes in different types of HPT, however, is not well understood. Bone mineral density (BMD) was measured in the distal radius, total body, femoral neck, and lumbar spine by dual energy x-ray absorptiometry in four groups of patients with different hyperparathyroid conditions: primary symptomatic HPT (n = 54), primary asymptomatic (mild) HPT (n = 24), HPT associated with hemodialysis (n = 20), and HPT associated with renal transplant (n = 30). Subsets of patients with primary symptomatic HPT (n = 52), HPT associated with hemodialysis (n = 19), and HPT associated with renal transplant (n = 15) underwent parathyroidectomy, and bone density was measured longitudinally for 3 yr. Patients with primary asymptomatic (mild) HPT did not undergo surgery and were followed prospectively. Before surgery, all groups showed a greater reduction of bone mineral density in cortical bone (distal radius) than in predominantly trabecular bone (lumbar spine). In primary symptomatic HPT, the BMD z-score of the distal radius was -1.80 +/- 0.21 (+/-SEM), and the corresponding figures for the total body, femoral neck, and lumbar spine were -0.60 +/- 0.15, -0.54 +/- 0.14, and -0.53 +/- 0.18 compared with those of an age- and sex-matched reference group. In renal HPT BMD z-scores were -2.51 +/- 0.38 (hemodialysis patients) and -2.83 +/- 0.43 (renal transplant patients) for the distal radius and between -0.81 and -1.46 for the other measured sites. After parathyroidectomy, BMD increased by 1-8% at all sites in patients with primary symptomatic HPT and HPT associated with renal transplant. The largest increase in bone mass was observed in patients with HPT associated with hemodialysis, in whom the improvement amounted to 7-23%. In patients with primary HPT and HPT associated with hemodialysis, this increase in bone density resulted in virtual recovery from their preoperative bone loss. The majority of patients with asymptomatic primary HPT disease (n = 21) maintained their bone density during the follow-up period and have not shown evidence of increases in serum calcium or PTH levels, but three patients followed conservatively underwent parathyroidectomy due to progressive deterioration of BMD. We conclude that, regardless of the etiology, a large proportion of HPT patients show reduced bone density. In patients with primary symptomatic HPT and patients with HPT associated with hemodialysis, bone density increases after parathyroidectomy to an extent that largely restores the preoperative bone loss. However, no anabolic effect of parathyroidectomy on bone mass was observed in patients with HPT associated with renal transplant, probably because of their immunosuppressive therapy.