Primary Hyperparathyroidism (PHPT)

• Definition of problem:
  • Primary hyperparathyroidism (PHPT):
    • Is the unregulated overproduction of parathyroid hormone (PTH) resulting in abnormal calcium homeostasis
• Frequency:
  • Primary hyperparathyroidism is more common in women:
    • The incidence being:
      • 66 per 100,000 person-years in females
      • 25 per 100,000 person-years in males
  • In a large study of 3.5 million enrollees in Kaiser Permanente of Southern California:
    • The incidence fluctuated over time but was not seen to decrease substantially​
    • On the contrary, the prevalence of primary hyperparathyroidism saw a substantial increase in this population
  • The mean age at diagnosis has remained between:
    • 52 and 56 years
• Etiology:
  • In approximately 85% to 90% of cases:
    • Primary hyperparathyroidism is caused by:
      • A single adenoma
  • In 15% of cases:
    • Multiple glands are involved:
      • Multiple adenomas:
        • Doble adenomas
        • Triple adenomas
      • Hyperplasia (4 glands)
  • Rarely, primary hyperparathyroidism is caused by parathyroid carcinoma
  • The etiology of adenomas or hyperplasia:
    • Remains unknown in most cases
  • Familial cases can occur as either part of the:
    • Multiple endocrine neoplasia syndromes (MEN 1 or MEN 2a)
    • Hyperparathyroid-jaw tumor (HPT-JT) syndrome
    • Familial isolated hyperparathyroidism (FIHPT)
    • Familial hypocalciuric hypercalcemia and neonatal severe hyperparathyroidism also belong to this category
  • The molecular genetic basis of MEN 1 (Wermer Syndrome):
    • Is an inactivating mutation of the MEN1 gene:
      • Located on chromosome band 11q13
  • MEN 2a is caused by a:
    • Germline mutation of the Ret proto-oncogene on chromosome 10. 
  • Germline mutation of HRPT2 localized on chromosome arm 1q:
    • Is responsible for HPT-JT
• While FIHPT is genetically heterogeneous

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