Bone histomorphometry in hemodialysed patients.

We performed bone histomorphometry in thirty hemodialysed patients. Ten patients had a double iliac bone biopsy to estimate bone histomorphometry reproductibility. There was no difference between the mean results for each of the 10 patients at each site. However, there was an intra-individual variation which was small for the parameters of formation and particularly osteoid thickness and mineralizing rate and greater for resorption parameters. Mineralization rate appeared the most reliable and discriminant parameter. These 30 patients were separated in two groups according to their mineralizing rate (MR); patients with an MR greater than 0.3 mu/day were in group I and had severe hyperparathyroidism without major impairment of bone mineralization and high formation rate. They also had high serum alkaline phosphatases and high serum parathyroid levels measured with a COOH terminal antibody (iPTH). Patients with a low MR less than 0.3 mu/day (group II) had a severe mineralization defect with low formation rate, normal alkaline phosphatase and significantly lower levels of iPTH than in group I. This last type of histological bone lesion could not be due to aluminum intoxication since the level of serum aluminum was the same in the two groups. The mineralizing defect appeared to be inversely correlated with the percent of osteoid surfaces covered by osteoblast and with the iPTH level. These data suggest that during the course of renal osteodystrophy PTH stimulates not only bone resorption but also bone mineralization by increasing osteoblastic number.