Endocrine: Secondary & Tertiary Hyperparathyroidism

Secondary Hyperparathyroidism

Definition/Causes

  • Definition: Disease Outside of the Parathyroid Gland Causes Hypersecretion of PTH
    • Induces Cell Proliferation in All Four Glands
  • Causes:
    • Chronic Kidney Disease (Most Common)
      • Unable to Hydroxylate Calcium
      • Develops in 90% of Patients with Renal Failure By the Time Hemodialysis is Required
    • Malabsorption of Calcium/Vitamin D
  • Chronic Disease Increases Risk for Osteoporosis

Diagnosis/Labs

  • Low Calcium
  • High Phosphorous
  • High PTH

Treatment

  • Initial Treatment: Medical (Compared to Tertiary Hyperparathyroidism)
  • Medical Management:
    • Calcium & Vitamin D Supplementation
    • Phosphate Binders
    • Cinacalcet: Calcimimetic (Mimics Calcium) to Activate Ca-Sensing Parathyroid Receptors & Inhibit PTH Production
  • Subtotal/Total Parathyroidectomy Indications:
    • Symptoms of Hyperparathyroidism:
      • Bone Pain or Pathologic Fracture
      • Pruritis
      • Nephrolithiasis
      • Fatigue or Mental Status Changes
    • Patient Preference
    • Calciphylaxis
    • Failure of Medical Management with:
      • Hypercalcemia
      • Hypercalciuria
      • PTH > 800 pg/mL
      • Hyperphosphatemia
      • Osteoporosis

Tertiary Hyperparathyroidism

Definition/Causes

  • Definition: Autonomously Hyperfunctioning Parathyroid Glands that Function Outside of Normal Feedback Controls
  • Causes:
    • Long-Standing Secondary Hyperparathyroidism After Renal Transplant (By Far the Most Common)
      • Risk After Renal Transplant: 20-50%
    • Chronic Phosphate Treatment (Hypophosphatemic Rickets)

Pathophysiology

  • Decreased Expression of Extracellular Calcium-Sensing Receptors
  • Decreased Density of Vitamin D Receptors
  • Decreased Expression of Klotho & Fibroblast Growth Factor Receptor 1

Diagnosis/Labs

  • High PTH
  • Normal-High Calcium
  • Normal-Low Phosphorous

Treatment

  • Primary Treatment: Surgical (Compared to Secondary Hyperparathyroidism)
    • May Consider Medical Therapy in Select Patients Although the Treatment for Tertiary Hyperparathyroidism is Primarily Surgical
  • Subtotal/Total Parathyroidectomy Indications:
    • Symptoms of Hyperparathyroidism:
      • Bone Pain or Pathologic Fracture
      • Pruritis
      • Nephrolithiasis
      • Fatigue or Mental Status Changes
    • Severe Hypercalcemia (Ca > 12 mg/dL)
    • Persistent Hypercalcemia (Ca > 10.2 mg/dL for > 3 Months Postoperatively)
    • Osteoporosis