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Snapshot
  • 55-year-old woman has hypercalcemia discovered as an incidental finding during normal routine physical examination. A hand radiograph is shown at right.
Introduction
  • Increased parathyroid hormone (PTH) production that may be of primary, secondary or tertiary causes
  • Pathophysiology
    • PTH indirectly stimulates osteoclasts by binding to its receptor on osteoblasts, inducing RANK-L and M-CSF synthesis
  • Epidemiology
    • occurs in 0.1% of the population
    • 90% result from a single adenoma
    • remaining 10% from parathyroid hyperplasia
    • parathyroid carcinoma accounts for less than 1% of all cases
Classification
  • Primary 
    • typically the result of hypersecretion of PTH by a parathyroid adenoma/hyperplasia
    • may result in osteitis fibrosa cystica
      • breakdown of bone
      • common involves the jaw
  • Secondary
    • secondary parathyroid hyperplasia as compensation from hypocalcemia or hyperphosphatemia
      • ↓ gut Ca2+ absorption
      • ↑ phosphorous
    • associated conditions
      • chronic renal disease
        • renal disease causes hypovitaminosis D
          • leads to ↓ Ca2+ absorption 
      • renal osteodystrophy
        • bone lesions due to secondary hyperparathyroidism 
  • Tertiary
    • parathyroid glands become dysregulated after secondary hyperparathyroidism
      • secrete PTH regardless of Ca2+ level
     
    Serum Ca
    Serum Phos
    Serum PTH
    Primary
    Secondary
    normal or ↓
    Tertiary
Presentation
  • Symptoms
    • often asymptomatic
    • weakness
    • kidney stones ("stones")
    • bone pain ("bones")
    • constipations ("groans")
Evaluation
  • Serology
    • primary
      • hypercalcemia
      • ↑ PTH
    • secondary
      • hypocalcemia/normocalcemia 
      • ↑ PTH
    • malignancy
      • ↓ PTH
    • ↑ alkaline phosphatase
    • normal anion gap metabolic acidosis
      • ↓ renal reclamation of bicarbonate
  • Urinalysis
    • primary
      • hypercalciuria (renal stones)
      • ↑ cAMP
  • Radiograph
    • cystic bone spaces ("salt and pepper")
      • often in the skull
    • loss of phalange bone mass
      • ↑ concavity (see key image of this topic)
    • subperiosteal thinning (cortical resorption) 
  • EKG
    • shortened QT
Treatment
  • Operative
    • resect adenoma/hyperplastic glands
      • indications
        • primary hyperparathyroidism with adenoma
      • outcome
        • curative if present
  • Pharmacologic
    • hydration followed by furosemide
      • ↑ excretion of calcium
    • bisphosphonates
    • cinacalcet 
      • calcium mimetic that decreases PTH production in the parathyroid glands
Complications
  • Peptic ulcer disease
    • ↑ gastrin production stimulated by ↑ Ca2+
  • Acute pancreatitis
    • ↑ lipase activity stimulated by ↑ Ca2+
  • CNS dysfunction
    • anxiety, confusion, coma
    • result of metastatic calcification of the brain
 

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