Generalities of Hyperparathyroidism

• Single gland adenoma is the most common cause:
  • (75% to 90% of the cases of PHPT
• Lower pole adenomas (in relation to the thyroid):
  • Are more common than are upper pole adenomas
• The average size of a parathyroid gland is:
  • 6 mm X 4 mm X 2 mm
• The sizes of a parathyroid adenoma range from:
  • 1 cm to 3 cm
• The normal weight of a parathyroid gland is:
  • Approximately 40 mg to 50 mg
• The weight of parathyroid adenomas vary between:
  • 553.7 +/- 520.5 mg (range, 66-2536)
• Ectopic glands can be present in:
  • 4% to 16% of cases
• PHPT is caused by:
  • The enlargement of a single parathyroid gland or parathyroid adenoma in approximately 75% to 90% of the cases
  • Multi-disease is seen in 15% to 25% of the cases:
    • Double adenomas:
      • Are seen in approximately 2% to 12% of the cases
    • Triple adenomas:
      • In less than 1% the cases (0.2%)
    • Four adenomas or parathyroid gland hyperplasia:
      • In less than 3% to 15% of the cases
  • Parathyroid carcinoma as the cause of PHPT is extremely rare in most parts of the world (~1%)
• Most parathyroid adenomas consist of parathyroid chief cells:
  • They are usually encapsulated
  • In 50% of the cases they are surrounded by normal parathyroid tissue
• Some adenomas, nevertheless, are composed of oxyphil cells
  • These adenomas are usually larger than chief cell adenomas
• Parathyroid adenomas are sometimes located within the thymus:
  • They express a parathyroid-specific gene:
    • GCMB:
      • Contrasting with the normal thymus:
        • Which does not express neither PTH nor GCMB
• In a study by Ruda et al:
  • 20, 225 patients with PHPT:
  • Parathyroid hyperplasia accounted for approximately six percent of cases
  • In parathyroid hyperplasia all four glands are enlarged:
    • With the lower glands typically being larger than the upper ones
    • The glands are usually composed of chief cells
    • Clear cell hyperplasia is very rare:
      • And is the only form in which the upper glands are larger than the lower ones

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