What is the evaluation and management approach for hyperparathyroidism?

Evaluation and Management of Hyperparathyroidism

Hyperparathyroidism should be managed with a combination of medical therapy and surgical intervention based on disease severity, with parathyroidectomy recommended for patients with severe hyperparathyroidism (persistent serum intact PTH >800 pg/mL) associated with hypercalcemia and/or hyperphosphatemia refractory to medical therapy. 1

Diagnostic Evaluation

Laboratory Assessment

• Serum calcium (ionized or total with albumin correction)
• Intact parathyroid hormone (iPTH)
• Serum phosphorus
• 25-OH Vitamin D (to exclude vitamin D deficiency as a secondary cause)
• Serum alkaline phosphatase (marker of bone turnover)
• Total CO2 (to assess for metabolic acidosis)

Imaging Studies (for surgical planning)

• Ultrasound of the neck
• 99mTc-sestamibi scintigraphy with SPECT/CT (parathyroid scan)
• Additional imaging (CT scan or MRI) for re-exploration cases 1

Classification and Management Approach

1. Primary Hyperparathyroidism

Primary hyperparathyroidism is characterized by autonomous PTH secretion resulting in hypercalcemia.

Medical Management:

• Indicated for patients who:

  • Refuse surgery
  • Have prohibitive surgical risks due to comorbidities
  • Require management of hypercalcemia before surgery 2

• Options include:

  • Cinacalcet: Increases sensitivity of calcium-sensing receptors
    • Starting dose: Individualized based on calcium levels
    • Titrate to normalize serum calcium
    • Monitor for side effects (nausea, vomiting) 3, 2
  • Bisphosphonates: For bone protection
  • Adequate hydration
  • Avoid thiazide diuretics

Surgical Management:

• Definitive treatment is surgical excision of abnormal parathyroid tissue 1
• Indications for surgery:
  • Symptomatic hypercalcemia
  • Serum calcium >1 mg/dL above normal range
  • Reduced bone mineral density (T-score <-2.5)
  • Age <50 years
  • Kidney stones or nephrocalcinosis
  • Creatinine clearance <60 mL/min

2. Secondary Hyperparathyroidism in Chronic Kidney Disease

Secondary hyperparathyroidism occurs due to chronic kidney disease with resulting phosphate retention, hypocalcemia, and vitamin D deficiency.

Medical Management:

• Control serum phosphorus:

  • Dietary phosphate restriction
  • Phosphate binders

• Correct hypocalcemia:

  • Calcium supplements (if needed)
  • Maintain serum calcium in normal range

• Vitamin D therapy:

  • For patients with PTH >300 pg/mL, use active vitamin D sterols 1
  • Options include:
    • Calcitriol: 0.5-1.0 μg orally 2-3 times weekly or 0.25 μg daily
    • Doxercalciferol: 2.5-5.0 μg orally 2-3 times weekly
    • Paricalcitol: For patients with elevated calcium or phosphorus 1

• Monitor response:

  • Check calcium and phosphorus every 2 weeks for first month, then monthly
  • Check PTH monthly for 3 months, then quarterly once target levels achieved
  • Target PTH: 150-300 pg/mL for dialysis patients 1

Surgical Management:

• Indications for parathyroidectomy:

  • Persistent serum iPTH >800 pg/mL with hypercalcemia/hyperphosphatemia refractory to medical therapy
  • Calciphylaxis with elevated PTH (>500 pg/mL)
  • Development of tertiary hyperparathyroidism 1

• Surgical options:

  • Subtotal parathyroidectomy
  • Total parathyroidectomy with autotransplantation
  • Include transcervical thymectomy to remove potential supernumerary glands 1

3. Tertiary Hyperparathyroidism

Tertiary hyperparathyroidism occurs when autonomous parathyroid function persists after correction of the underlying cause of secondary hyperparathyroidism (typically after kidney transplantation).

Management:

• Primary treatment is surgical parathyroidectomy 4
• Cinacalcet may be used in patients not suitable for surgery

Post-Parathyroidectomy Management

1. Monitor ionized calcium every 4-6 hours for first 48-72 hours, then twice daily until stable 1

2. For hypocalcemia (ionized calcium <0.9 mmol/L):

   • Calcium gluconate infusion: 1-2 mg elemental calcium/kg/hour
   • Adjust to maintain normal ionized calcium (1.15-1.36 mmol/L) 1

3. When oral intake is possible:

   • Calcium carbonate: 1-2 g three times daily
   • Calcitriol: Up to 2 μg/day
   • Adjust to maintain normal calcium levels 1

4. Reassess need for phosphate binders or potential need for phosphate supplements 1

Common Pitfalls and Caveats

1. Vitamin D deficiency: Always check 25-OH vitamin D levels, as deficiency can cause secondary hyperparathyroidism that may be mistaken for primary disease 1

2. Medication interactions: Cinacalcet can cause hypocalcemia and QT interval prolongation; use with caution 1

3. Post-surgical complications: Hungry bone syndrome can cause severe hypocalcemia after parathyroidectomy, requiring aggressive calcium and vitamin D supplementation

4. Metabolic acidosis: Maintain serum total CO2 >22 mEq/L to prevent exacerbation of bone disease in CKD patients 1

5. Parathyroid imaging: Not routinely needed for first-time surgery but essential for re-exploration cases 1

By following this systematic approach to evaluation and management, hyperparathyroidism can be effectively controlled, reducing the risk of complications such as bone disease, kidney stones, and cardiovascular events.