CKD-MBD is classified into four major histological groups (in terms of turnover, mineralization and volume): hyperparathyroid bone disease (high turnover disease, with normal mineralization and variable volume); adynamic bone disease (low turnover disease, with normal mineralization and decreased bone volume); osteomalacia (low turnover disease, with reduced mineralization and with normal or high bone volume); and mixed renal osteodystrophy (reduced mineralization with or without increased bone formation).