What is the appropriate management for a 67-year-old man with stage 4 chronic kidney disease (eGFR ≈ 28 mL/min/1.73 m²), normal ionized calcium, and elevated intact parathyroid hormone?

Management of Secondary Hyperparathyroidism in Stage 4 CKD

This 67-year-old man with stage 4 CKD (eGFR 28), normal ionized calcium (1.26 mmol/L), and mildly elevated PTH (111.3 pg/mL) requires immediate nephrology referral, monitoring of mineral metabolism every 3 months, and correction of vitamin D deficiency if present—but does NOT yet require activated vitamin D therapy because his PTH is below the treatment threshold.

Immediate Action: Nephrology Referral

• All patients with eGFR <30 mL/min/1.73 m² require immediate nephrology referral to prepare for potential renal replacement therapy and manage complex CKD complications. 1
• Referral at this stage reduces costs, improves quality of care, and delays dialysis initiation. 1
• Begin structured education about dialysis and transplantation options now, as preparation takes months and progression rates are unpredictable. 1

Assessment of Mineral-Bone Disorder

Current Laboratory Interpretation

• The ionized calcium of 1.26 mmol/L (approximately 5.04 mg/dL) is normal, indicating adequate calcium homeostasis despite reduced kidney function. 2
• The PTH of 111.3 pg/mL is mildly elevated but does NOT meet the treatment threshold for stage 4 CKD, where intervention is typically considered when PTH >300 pg/mL. 3
• In CKD, normal calcium reabsorption requires higher PTH levels than in healthy individuals—this is an adaptive response, not necessarily pathologic. 2

Required Baseline Testing

Before initiating any therapy, obtain the following laboratory studies (if not already available): 4

• Serum calcium and phosphorus (already have ionized calcium; verify total calcium and phosphorus)
• 25-hydroxyvitamin D level to assess for nutritional vitamin D deficiency
• Alkaline phosphatase to evaluate bone turnover
• Serum bicarbonate to screen for metabolic acidosis

Monitoring Schedule for Stage 4 CKD

For patients with eGFR <30 mL/min/1.73 m² (stage 4-5 CKD), establish the following monitoring protocol: 4

Parameter	Frequency	Target/Action Threshold
Serum calcium & phosphorus	Every 3 months	Ca: 8.5-10.5 mg/dL; PO₄: <4.5 mg/dL
Intact PTH	Every 3 months	Stage 4 target: 70-110 pg/mL
Hemoglobin	Every 3 months	>12 g/dL (women), >13 g/dL (men)
Serum bicarbonate	Every 3 months	≥22 mmol/L
Blood pressure	Every clinical visit	<140/90 mmHg (or <120/80 if tolerated)

Vitamin D Assessment and Repletion

Step 1: Measure 25-Hydroxyvitamin D

• Check 25(OH)D level immediately—CKD patients have 80-90% prevalence of vitamin D insufficiency (<30 ng/mL). 3
• The target 25(OH)D level is ≥30 ng/mL to prevent secondary hyperparathyroidism and skeletal complications. 3

Step 2: Nutritional Vitamin D Supplementation (If Deficient)

If 25(OH)D is <30 ng/mL, initiate ergocalciferol (vitamin D₂): 4, 3

• Ergocalciferol 50,000 IU orally once weekly for 12 weeks, then monthly maintenance dosing
• This is the preferred regimen for documented deficiency in CKD according to K/DOQI guidelines 3
• Re-measure 25(OH)D at 3 months to confirm adequate response 3

If 25(OH)D is ≥30 ng/mL, provide maintenance supplementation: 3

• Cholecalciferol (vitamin D₃) 800 IU daily for patients >60 years old
• This prevents recurrent deficiency

Critical Distinction: Do NOT Use Activated Vitamin D Yet

• Activated vitamin D (calcitriol, doxercalciferol, paricalcitol) is NOT indicated at this time because: 3, 5

  • PTH is only 111.3 pg/mL (below the 300 pg/mL threshold for stage 4 CKD)
  • Ionized calcium is normal
  • The 2017 KDIGO guideline recommends against routine use of activated vitamin D in CKD stages 3-4 patients not on dialysis 3

• Activated vitamin D should only be considered if ALL of the following criteria are met after 3-6 months of nutritional vitamin D repletion: 3

  1. Intact PTH >300 pg/mL (persistently elevated above target)
  2. 25-hydroxyvitamin D ≥30 ng/mL (nutritional deficiency corrected)
  3. Serum calcium <9.5 mg/dL (no hypercalcemia)
  4. Serum phosphorus <4.6 mg/dL (no hyperphosphatemia)

Management of Other CKD Complications

Metabolic Acidosis

• Monitor serum bicarbonate every 3 months; if <22 mmol/L, initiate sodium bicarbonate supplementation to correct chronic metabolic acidosis. 4

Hyperphosphatemia (If Present)

• If serum phosphorus >4.5 mg/dL, initiate a low-phosphorus diet (800-1000 mg/day) for one month, then recheck. 4
• If phosphorus remains >4.5 mg/dL despite dietary restriction, start a phosphate binder. 4
• Avoid calcium-based phosphate binders if activated vitamin D is eventually needed, as this combination markedly increases hypercalcemia risk. 3

Anemia Screening

• Check hemoglobin every 3 months; if <12 g/dL (women) or <13 g/dL (men), perform complete anemia workup including iron studies. 4
• Treat iron deficiency if identified; if anemia persists despite adequate iron stores, initiate erythropoiesis-stimulating agent. 4

Blood Pressure Control

• Target systolic blood pressure <140/90 mmHg (or <120/80 mmHg if tolerated using standardized office measurement). 1
• Use ACE inhibitor or ARB as first-line therapy, titrated to maximum tolerated dose. 1

Medication Safety

• Verify appropriate dosing of all medications for eGFR 28 mL/min/1.73 m². 4
• Avoid nephrotoxic agents: NSAIDs, COX-2 inhibitors, iodinated contrast media. 1
• If the patient has diabetes, reduce metformin dose to ≤1000 mg daily or discontinue (eGFR <30 is below safe threshold). 1

Common Pitfalls to Avoid

• Do not start activated vitamin D (calcitriol) simply because PTH is above the normal range—mild PTH elevation is expected and adaptive in stage 4 CKD; treatment thresholds are much higher (>300 pg/mL). 3
• Do not assume vitamin D3 is "safe" without monitoring—even nutritional vitamin D can cause hypercalcemia in CKD due to impaired calcium handling. 3
• Do not ignore the calcium-phosphorus product—maintain Ca × P product <55 mg²/dL² to prevent soft tissue calcification. 3
• Do not delay nephrology referral—stage 4 CKD requires specialist co-management regardless of how "stable" the patient appears. 1

When to Escalate Therapy

Re-evaluate PTH, calcium, and phosphorus in 3 months. If at that time: 3

• PTH has risen to >300 pg/mL AND
• 25(OH)D is ≥30 ng/mL AND
• Calcium <9.5 mg/dL AND
• Phosphorus <4.6 mg/dL

Then consider initiating low-dose activated vitamin D (e.g., doxercalciferol 1 mcg daily for stage 3-4 CKD per FDA labeling). 5

Monitor calcium and phosphorus monthly for 3 months after starting activated vitamin D, then quarterly; discontinue if calcium exceeds 10.2 mg/dL. 3