13- PTH

• Parathyroid hormone

  Increases calcium concentration by:

  • Stimulation of Ca reabsorption by kidney
  • Activation of vitamin D → ↑ intestinal Ca absorption
  • Stimulation of osteoclasts → ↑ Ca release from bone

  Decreases phosphate by ↑ kidney excretion
• Vitamin D

  Increases both calcium and phosphate
• Hypoparathyroidism


  • Causes: Head and neck surgeries most commonly-thyroidectomy (non-surgical causes are rare: autoimmune, congenital)
• Hyperparathyroidism

  • Causes:
  • Primary (may be associated with MEN syndrome):
  • Solitary adenoma (85%)
  • Hyperplasia of all 4 glands (15%)
  • Parathyroid malignancy (1%)
• Hypoparathyroidism - Clinical features

  Symptoms of hypocalcemia, which may be variably symptomatic
• Hyperparathyroidism - Clinical features

  Primary hyperparathyroidism often have asymptomatic elevated Calcium (found incidentally in routine blood testing)

  When symptomatic → symptoms of hypercalcemia (stones, bones, groans, and psychiatric overtones)
• Hypoparathyroidism - Diagnosis

  • Low serum calcium
  • High serum phosphate
  • Serum PTH inappropriately low
  • Low urine cAMP
  • ECG: long Qt
• Hyperparathyroidism - Diagnosis

  • Increased calcium levels
  • Increased PTH levels
  • Hypophosphatemia
  • Hypercalciuria
  • High urine cAMP
  • Elevated BUN & creatinine
  • ECG: short QT
  • Radiography: Osteopenia (bone x-ray is not a good test for bone effects of high PTH → DEXA densitometry is better)
• Hypoparathyroidism - Treatment

  IV calcium gluconate in severe cases, oral calcium in mild to moderate cases.

  2. Vitamin D supplementation (calcitriol).

  *look for urinary stones*
• Hyperparathyroidism - Treatment

  Surgery is the only definitive treatment, but not all patients require it. If the patient is over 50 years of age and is asymptomatic (with normal bone mass and renal function), surgery may not be needed.

  If surgery is not possible: cinacalcet → inhibits PTH release.