Parathyroid Glands

  • Through their secretion of parathyroid hormone (PTH):
    • The parathyroid glands are primarily responsible for:
      • Maintaining extracellular calcium concentrations
  • Hyperparathyroidism:
    • Is a disease characterized by excessive secretion of parathyroid hormone:
      • An 84–amino acid polypeptide hormone
  • The secretion of parathyroid hormone:
    • Is regulated directly by the plasma concentration of ionized calcium
  • The main effects of parathyroid hormone (PTH):
    • Are to increase the concentration of plasma calcium:
      • By increasing the release of calcium and phosphate:
        • From bone matrix
      • Increasing calcium reabsorption:
        • By the kidney
      • Increasing renal production of:
        • 1,25-dihydroxyvitamin D-3 (calcitriol):
          • Which increases intestinal absorption of calcium
    • Thus, overproduction of parathyroid hormone results in:
      • Elevated levels of plasma calcium
  • Parathyroid hormone also causes phosphaturia:
    • Thereby decreasing serum phosphate levels
  • Hyperparathyroidism is usually subdivided into:
    • Primary, secondary, and tertiary hyperparathyroidism
  • Usually, four parathyroid glands are situated posterior to the thyroid gland:
    • A small number of patients have 3, 5, or, occasionally, more glands:
      • The glands are identified based on their location as right or left and superior or inferior.
  • The inferior glands are derived from:
    • The third pharyngeal pouch:
      • This structure is also the embryologic origin of the thymus:
        • Therefore, the inferior glands originate more cephalad than the superior glands:
          • But they migrate along with the thymus to finally become situated more inferiorly than the superior glands
        • Because of their embryologic association with the thymus:
          • The inferior glands are often found adjacent to or within the thymus
          • They are usually located near the inferior pole of the thyroid
  • The superior glands are more consistent in location:
    • Usually found just superior to the intersection of the inferior thyroid artery and the recurrent laryngeal nerve
    • The superior glands are derived embryologically from the fourth pharyngeal pouch:
      • This structure also gives rise to the C cells of the thyroid gland
    • Because of their embryologic origin, the superior glands are occasionally found within the substance of the thyroid gland

#Arrangoiz #ParathyroidSurgeon #ParathyroidSurgeon #HeadandNeckSurgeon #EndocrineSurgery #Hyperparathyroidism #MSMC #MountSinaiMedicalCenter #Mexico #Miami

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