In hyperparathyroidism, the principally affected sites are where the bone turnover is most active, for example the trabecular bone of the vertebrae, the phalanges, the ends of long bones and parts of the skull.
Macroscopically there is demineralisation of bone. Increased bone reabsorption leads to subperiosteal resorption of the phalanges, thinning of the cortex, and the formation of bone cysts or brown tumours. Deformities can lead to fracture or bending.
Microscopically there is an increased number of osteoclasts which increase the amount of bone resorption. The marrow spaces are filled with fibrous tissue producing osteitis fibrosa.
The increased osteoblast activity causes an increased woven - non-lamellar - bone trabeculae.
Last reviewed 01/2018