Decreased mineralization in hemodialysis patients after subtotal parathyroidectomy

Many hemodialysis patients undergo subtotal parathyroidectomy (sPTx) because of the complications of severe secondary hyperparathyroidism. In some patients, however, renal osteodystrophy fails to regress. In uremia, the high levels of circulating immunoreactive parathyroid hormone (iPTH) which accompany osteitis fibrosa are associated with accelerated bone formation. After sPTx, the fall in iPTH may decrease mineralization and increase osteoid formation. Bone histomorphometry, densitometry, and serum biochemical determinations were done in 20 patients on regular maintenance hemodialysis and after sPTx in 3 additional patients. Densitometry at the radial diaphysis was inversely related to osteoid volume so that low bone mineral content indicated excess osteoid. Elevated serum alkaline phosphatase activity was associated with osteitis fibrosa. Tetracycline double labels identified 5 patients with an increased rate of mineralization. Levels of iPTH and serum phosphorus were positively correlated to the mineralization rate. The fall in iPTH after sPTx was accompanied by a reduction in osteitis fibrosa and decreased mineralization. The nonosteoblastic osteoid became more abundant. After sPTx some hemodialysis patients may convert the osteitis fibrosa to a poorly treatable low turnover osteomalacia.