Skeletal Manifestations of Primary Hyperparathyroidism (PHPT)

• Skeletal manifestations including osteopenia, osteoporosis, and osteitis fibrosa cystica:
  • Are found in approximately 15% of patients with PHPT
• PHPT is linked with a reduction in bone mineral density (BMD):
  • Particularly in the cortical bone:
    • Such as in the distal third of the radius
  • In the lumbar region, composed all most exclusively by trabecular bone, and in the femoral region, composed by cortical and trabecular bone:
    • The decrease in BMD is less severe
• Osteitis fibrosa cystica:
  • A skeletal manifestation that is rarely seen today:
    • Seen in less than five percent of patients with PHPT
  • Is caused by an increase in bone turnover:
    • Can be determined by finding an:
      • Elevated serum alkaline phosphatase level
  • The radiologic findings seen in patients with PHPT with bone disease are characterized by:
    • Subperiosteal resorption:
      • Most obvious on the radial aspect of the middle phalanx of the second and third fingers
    • Bone cysts
    • Tufting of the distal phalanges:
      • Which are best evaluated on plain x-rays of the hands
    • Brown or osteoclastic tumors:
      • Caused by the accumulations of osteoclasts and fibrous tissue:
      • Brown tumors have a slightly greater incidence in PHPT than in secondary HPT:
        • 3% versus 2%
      • In patients with chronic kidney disease:
        • Persistent and excessive urinary calcium elimination:
          • Can lower serum calcium level:
            • And lead to an increase in PTH secretion
      • This results in mobilization of calcium from the bones:
        • Through rapid osteoclastic turnover of bone to maintain normal serum calcium levels
      • In regions where bone loss is exceptionally fast:
        • Hemorrhage, and reparative granulation tissue, with active, vascular, proliferating fibrous tissue may replace the normal marrow contents:
          • Resulting in a brown tumor
      • Hemosiderin imparts the brown color (hence the name of the lesions
    • The skull also may be affected:
      • Appears mottled with a loss of definition of the inner and outer cortices
• Patients with normal serum alkaline phosphatase levels:
  • Almost never have clinically apparent osteitis fibrosa cystica
• Bone disease correlates with serum PTH and vitamin D levels

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