Updated: 10/10/2016

Hyperparathyroidism

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https://upload.orthobullets.com/topic/9089/images/subperiosteal_resorption.jpg
Introduction
  • Increased parathyroid hormone (PTH) production that may be of primary, secondary or tertiary causes
  • Epidemiology 
    • incidence
      • occurs in 0.1% of the population
      • 90% result form a single adenoma
      • remaining 10% from parathyroid hyperplasia
    • demographics
      • more common in women
      • hyperparathyroidism and maligncacy make up the majority of patients with hypercalcemia
  • Pathophysiology
    • PTH indirectly stimulates osteoclasts by binding to its receptor on osteoblasts, inducing RANK-L and M-CSF synthesis 
    • Excessive PTH leads to over-stimulation of bone resorption
      • cortical bone affected more than cancellous
  • Associated conditions
    • Brown tumor
      • resembles a giant cell tumor of bone relating to focal demineralization of bone in the setting of hyperparathyroidism.
Classification
  • Primary
    • typically the result of hypersecretion of PTH by a parathyroid adenoma/hyperplasia
    • may result in osteitis fibrosa cystica
      • breakdown of bone, predominently subperiosteal bone
      • commonly 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 leisons 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")
    • uncommon cause of secondary hypertension
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)
  • EKG
    • shortened QT
Treatment
  • Acute hypercalcemia
    • IV fluids
    • Loop diuretics
  • Symptomatic hypercalcemia is treated surgically
    • treat with parathyroidectoy
    • complications include post-op hypocalcemia
    • manifests as numbness, tingling, and muscle cramps
    • should be treated with IV calcium gluconate 
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
  • Osteoporsis
    • Bone loss occurs as result of bone resorption due to excess PTH
 

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