My Clinical Notes

• Can be divided into primary and secondary
  • Primary hyperparathyroidism results from autonomous hyperplasia or a tumour of the parathyroid gland
  • Secondary hyperparathyroidism is commonly caused by prolonged states of hypocalcaemia resulting in compensatory hyper secretion of PTH
• Increased PTH acts on osteoblasts to release molecules which stimulate osteoclastic activity
• Skeletal classifications of hyperparathyroidism are therefore due to unabated osteoclastic bone resorption
• The entire skeleton is affected
• Anatomical changes associated with severe hyperparathyroidism are called osteitis fibrosa cystica occur rarely as it is currently diagnosed and treated at an early age
• The effects of secondary hyperparathyroidism are generally less severe than primary disease

 

Morphology

 

• Tends to affect cortical bone more severely than cancellous bone
• Subperiosteal reabsorption produces thinned cortices and loss of lamina dura around the teeth
• x-ray pattern which is virtually diagnostic is best seen along the radial aspect of the middle phalanges of the index and middle finger
• Characteristic of hyperparathyroidism are cortical cutting cones which are composed of a spearhead arrangement of osteoclasts that bore along and enlarge Haversian and Volkmann canals
• In cancellous bone the osteoclasts tunnel into and dissect centrally along the length of the trabeculae creating the appearance of railroad tracks and producing what is known as dissecting osteitis
• There is a decrease in bone density causing osteopenia
• At the same time there is increased osteoblastic activity
• Bone loss predisposes to microfractures and secondary haemorrhages that elicit an influx of multinucleated macrophages and an in growth of fibrous tissue creating a mass of reactive tissue called a brown tumour
• Generalised osteitis fibrosa cystica is associated with;
  • Increased bone cell activity
  • Peritrabecular fibrosis
  • Cystic brown tumours

 

• Control of parathyroidism allows bony changes to regress significantly or disappear completely

This entry was posted on Thursday, November 15th, 2007 at 2:12 pm and is filed under Orthopaedics. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.