What is the management approach for adynamic bone disease?

Management of Adynamic Bone Disease

The primary treatment approach for adynamic bone disease (ABD) is to increase bone turnover by allowing plasma intact PTH levels to rise, primarily through decreasing or eliminating calcium-based phosphate binders and vitamin D therapy. 1

Diagnostic Criteria

• Laboratory indicators for ABD:
  • Intact PTH < 100 pg/mL
  • Low bone alkaline phosphatase levels
• Gold standard for diagnosis: Histomorphometric analysis of tetracycline double-labeled bone biopsies 2
• Bone characteristics in ABD:
  • Low bone turnover
  • Low bone volume
  • Normal mineralization
  • Decreased cellularity with minimal/no fibrosis

Treatment Algorithm

Step 1: Modify Current Therapies

• Decrease or eliminate calcium-based phosphate binders 1
• Reduce or eliminate vitamin D therapy to allow PTH levels to rise 1
• Consider lowering dialysate calcium (1.0 to 2.0 mEq/L) to stimulate PTH secretion (note: this approach is considered experimental) 3, 1

Step 2: Monitor Treatment Response

• Target intact PTH levels to rise above 100-150 pg/mL 1, 4
  • If iPTH levels decrease below 150 pg/mL, reduce dose of cinacalcet and/or vitamin D sterols or discontinue therapy 4
• Monitor bone alkaline phosphatase as a marker of treatment response 1
• Regularly check serum calcium and phosphorus levels (at least every 3 months) 1
• Calculate calcium-phosphorus product (goal: <55 mg²/dL²) 1

Step 3: Manage Complications

• For hypercalcemia:
  • Discontinue vitamin D therapy if corrected total calcium exceeds 10.2 mg/dL 1
  • Consider non-calcium containing phosphate binders for phosphorus control 1
• For hyperphosphatemia:
  • Limit calcium supplementation (total elemental calcium intake should not exceed 2,000 mg/day from all sources) 1
  • Consider non-calcium containing phosphate binders 1

Important Considerations and Pitfalls

Risk Factors for ABD

• Calcium loading
• Advanced age
• Diabetes mellitus
• Hypogonadism
• Previous parathyroidectomy
• Peritoneal dialysis
• Antiresorptive therapies 2

Complications Associated with ABD

• Increased risk of fractures (4-fold increase in hip fracture risk compared to general population) 1
• Hypercalcemia due to impaired bone buffering capacity 1, 5
• Increased vascular calcification 5
• Potentially increased mortality rates 2

Medication Cautions

• Cinacalcet: Monitor for development of adynamic bone disease. If iPTH levels decrease below 150 pg/mL, reduce dose or discontinue therapy 4
• Avoid aluminum-containing phosphate binders: Aluminum overload can cause or worsen adynamic bone disease 1, 6
• Calcium-containing medications: May enhance vascular calcifications in the presence of adynamic bone disease 5

Monitoring Parameters

• Intact PTH levels (target: above 100-150 pg/mL) 1, 4
• Bone alkaline phosphatase 1
• Serum calcium and phosphorus (at least every 3 months) 1
• Calcium-phosphorus product (goal: <55 mg²/dL²) 1
• 25-hydroxyvitamin D levels (annually) 1
• Consider bone density testing if results will impact treatment decisions 1

Special Considerations

• Patients with oligoanuria may require further reduction in calcium intake due to limited ability to eliminate excess calcium 1
• Diabetic, elderly, and white patients may be at higher risk for developing ABD and require closer monitoring 2
• The relationship between low PTH, ABD, increased fracture risk, and vascular calcifications may explain the association with increased mortality 2