Large, rapid skeletal changes after parathyroidectomy

We report dramatic increases in spine and hip bone mineral density six weeks following parathyroidectomy in renal patients. We have previously reported a cross-sectional association between parathyroidectomy and higher axial bone mineral density in dialysis patients. Large axial increases in bone mineral density after surgery for primary hyperparathyroidism have been recorded by others at one year postoperatively. Bone mineral density was recorded before and six weeks after parathyroidectomy. Scans were performed at the lumbar spine, hip and non-dominant radius. Values were expressed as Z-scores (standard deviations from the mean of an age- and gender-matched reference population). Large increases in lumbar were spine and femoral neck bone mineral density seen at six weeks post parathyroidectomy. Median increases were 0.57 (p = 0.006) and 0.26 (p = 0.039) Z-score units for these sites, respectively. Individual six-week increases were as large as 1.3 Z-score units at the spine and 1.0 Z-score units at the femoral neck. No significant cohort change was detected at the forearm but individual forearm changes were highly variable. Several mechanisms to explain these large rapid increases can be postulated. These include: mineralization of osteoid and/or contraction of the remodeling space. The changes illustrate the extent to which the skeleton is capable of rapid and profound change in mineral content. Our findings emphasize that the skeleton is a heterogeneous organ and that bone density should be measured at multiple skeletal sites.