hyperparathyroidism
HYPERPARATHYROIDISM

Hyperparathyroidism is a condition wherein there is an excessive production of parathyroid hormone (PTH).

Primary hyperparathyroidism is the most common endocrine disorder and an important cause of hypercalcemia in ambulatory patients.

Classic signs and symptoms include bone disease, kidney stones and hypercalcinosis.

Primary goal of pharmacological therapy is to normalize calcium levels.

 

Principles of Therapy

  • Goal: Normalize calcium levels
  • Recommended for the following individuals:
    • Mildly elevated serum calcium levels (<1 mg/dL above upper normal limit)
    • No previous life-threatening hypercalcemic episodes
    • Normal bone & renal status
    • Clinically asymptomatic, >50 years old
    • Poor surgical candidate
    • Inability to undergo surgery
    • Patient preference

Pharmacotherapy

Bisphosphonates

  • Potent inhibitor of bone resorption
  • Useful to improve low bone mass in patients w/ untreated PHPT
  • Recommended for patients w/ PHPT & osteoporosis or those w/ low bone mineral density warranting intervention who opted not to undergo surgery
  • Increases bone mineral density after short term (2 years) therapy
  • Alternative treatment in mild hypercalcemia due to PHPT

Alendronate

  • Given to patients w/ mild PHPT for 1-2 years
  • Increased bone density at the hip & lumbar spine but not radius
  • Studies showed 10 mg/day Alendronate effectively reverses bone loss in hyperparathyroidism

Pamidronate

  • Most effective for acute treatment of hypercalcemia associated w/ PHPT
  • Given intravenously
  • Cannot be used as long-term treatment due to poor gastrointestinal drug absorption,
  • PTH levels increases w/ increased renal tubular resorption & gastrointestinal calcium absorption

Calcimimetic

  • Inhibits PTH secretion by activating calcium-sensing receptor in parathyroid gland
  • Used for poor surgical candidates to normalize serum calcium in patients w/ severe hypercalcemia
  • Preferred over bisphosphonates for patients who are unable to have surgery & whose primary indication for surgery is symptomatic &/or severe hypercalcemia w/ normal bone density

Cinacalcet

  • Approved use in PHPT
  • Only approved calcimimetic for secondary hyperparathyroidism treatment
  • Used to treat hyperparathyroidism in ESRD patients on long-term dialysis
  • Oral administration peaks within 2-3 hours which lowers circulating PTH levels within the same period
  • Reduces serum calcium levels in PTCA patients particularly in unresectable diseases & those who underwent multiple operations without cure

Vitamin D & Analogues

  • Aggressive supplementation is recommended for secondary hyperparathyroidism patients due to vitamin D deficiency w/ normal renal function
  • Helps in suppression of the synthesis of PTH
  • Inhibits evolution of parathyroid hyperplasia
  • Adequate daily intake of 200 IU, 400 IU & 600 IU are recommended for adults up to 50 years, 51-70 years & ≥71 years respectively
  • For patients w/ vitamin D deficiency, 50,000 IU weekly for 8 weeks or 3000 IU daily Vitamin D2 supplementation or 1000 IU daily Vitamin D3 is recommended
  • Caution must be observed as to high doses can lead to hypercalcemia
  • Vitamin D analogues (Paricalcitol & Doxercalciferol) are less likely to cause hypercalcemia
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