Hypervitaminosis D

• May be of dietary or iatrogenic origin (has narrow safety margin)
• Key features are hypercalcaemia with metastatic calcification of soft tissues
• Acute poisoning
  • In dogs and cats often from rodenticides containing cholecalciferol
  • Grossly:
    • Gastrointestinal haemorrhage
    • Foci of myocardial discoloration
  • Microscopically:
    • Mucosal haemorrhage
    • Necrosis of crypts
    • Focal myocardial necrosis
    • Mineralisation of intestinal mucosa, blood vessel walls, lungs and kidneys
• Chronic poisoning
  • Grossly:
    • Intense osteoclastic activity -> active resorption of bone, especially trabecular
  • Microscopically:
    • Excessive production of osteoid - appears both eosinophilic and basophilic in different places
    • Marrow cavity may be obliterated
    • Mineralisation of soft tissues, especially blood vessel walls
  • Due to inhibition of Parathyroid Hormone (PTH)|PTH and increase of calcitonin