Effects of parathyroidectomy on bone formation and mineralization in hemodialyzed patients

Abstract

Undecalcified sections of doubly tetracycline-labeled transiliac bone biopsy specimens obtained from 10 hemodialyzed patients before and 10 to 16 months after parathyroidectomy (PTX) were analyzed. Before parathyroidectomy (total PTX with autotransplant in 6 patients and subtotal PTX in 4 patients), all the patients demonstrated histological evidence of hyperparathyroidism with increased resorption parameters. A high bone formation rate (BFR) was noted in all patients but one who had both an increase in the osteoid seam thickness and a low calcification rate characteristic of osteomalacia. A significant correlation was found between immunoreactive parathyroid hormone (iPTH) levels and BFR at the tissue and at the basic multicellular unit (BMU) levels. Parathyroidectomy was associated with a dramatic drop in resorption surfaces and osteoclast number as well as in bone formation rate at the tissue, BMU, and cell levels. After PTX, the bone formation rate at the tissue level was low or in the lower range of normal values in 6 patients. The thickness index of osteoid seams was significantly reduced and no evidence of osteomalacia was present even in the 6 patients showing bone aluminum deposits after PTX. One of the 3 patients, who had an iPTH level within the normal range after PTX, showed an osteoid excess associated with a low bone formation rate. These data demonstrate that increased PTH secretion is an important factor of bone formation in dialyzed patients and that excessive reduction of the PTH secretion leads to an inactive bone.