What is the target intact parathyroid hormone (iPTH) range for an adult with chronic kidney disease stage 3‑5 (eGFR <60 mL/min/1.73 m²)?

Target iPTH in CKD Stages 3-5

For adults with CKD stages 3-5, target intact PTH levels should be maintained within stage-specific ranges: 35-70 pg/mL for stage 3,70-110 pg/mL for stage 4, and 150-300 pg/mL for stage 5 (dialysis patients). 1

Stage-Specific PTH Targets

The K/DOQI guidelines establish clear PTH targets that progressively increase as kidney function declines 1:

• CKD Stage 3 (GFR 30-59 mL/min/1.73 m²): 35-70 pg/mL 1
• CKD Stage 4 (GFR 15-29 mL/min/1.73 m²): 70-110 pg/mL 1
• CKD Stage 5 (GFR <15 or dialysis): 150-300 pg/mL 1, 2

Critical Rationale for Higher Targets in Advanced CKD

Do not attempt to normalize PTH to the general population reference range (<65 pg/mL) in dialysis patients, as this causes adynamic bone disease with increased fracture risk. 2 The elevated PTH targets in stage 5 CKD reflect the need to maintain adequate bone turnover in the setting of uremia 2, 3.

Evidence Supporting Stage 5 Targets

Research demonstrates that even when iPTH levels fall within the K/DOQI recommended range of 150-300 pg/mL for stage 5 patients, 88% still developed low-turnover bone disease, suggesting these targets may actually need to be higher rather than lower 3. This finding underscores that suppressing PTH too aggressively in dialysis patients is harmful 3.

Monitoring Frequency

Measurement frequency should be based on CKD stage 1:

• Stage 3: Measure calcium, phosphorus, and iPTH every 12 months 1
• Stage 4: Measure every 3 months 1
• Stage 5: Measure every 3 months 1, 2

More frequent monitoring (monthly for calcium/phosphorus, every 3 months for PTH) is required when patients are receiving active treatment with vitamin D sterols or phosphate binders 1.

When to Initiate Treatment Based on PTH

Early CKD (Stages 3-4)

PTH elevation begins when GFR falls below 60 mL/min/1.73 m², even when serum phosphorus remains normal 1. At these stages:

• First step: Check 25-hydroxyvitamin D levels and replete if <30 ng/mL with ergocalciferol 2
• Second step: Implement dietary phosphorus restriction to 800-1,000 mg/day when PTH exceeds target range 1
• Active vitamin D therapy (calcitriol) should only be initiated in stage 3 CKD when corrected calcium is <9.5 mg/dL, phosphorus is <4.6 mg/dL, and PTH remains elevated above target despite nutritional vitamin D repletion 1, 2

Advanced CKD (Stage 5/Dialysis)

For dialysis patients with PTH >300 pg/mL 2:

• Ensure phosphorus is controlled (<5.5 mg/dL) before starting active vitamin D 1, 2
• Initiate vitamin D sterols (calcitriol or paricalcitol) at low doses 1, 2
• If PTH remains >800 pg/mL despite optimized vitamin D therapy, add calcimimetics or consider parathyroidectomy 2

Common Pitfalls to Avoid

Never start active vitamin D therapy when phosphorus is elevated (>4.6 mg/dL in stages 3-4, >5.5 mg/dL in stage 5), as this worsens vascular calcification and increases the calcium-phosphate product. 2, 4 This is the most critical error in CKD-MBD management 2.

Do not target "normal" PTH levels in dialysis patients. The target of 150-300 pg/mL for stage 5 is intentionally 2-9 times the upper limit of normal to prevent adynamic bone disease 2, 5.

Recognize that PTH assays vary significantly between laboratories. Second-generation "intact PTH" assays overestimate biologically active PTH by detecting C-terminal fragments 2, 5. Use assay-specific reference ranges and follow trends rather than single values 5.

Alkaline Phosphatase as Adjunctive Marker

Measure alkaline phosphatase every 3-6 months when PTH is elevated 2. Rising alkaline phosphatase with elevated PTH suggests progressive high-turnover bone disease and adds predictive value for assessing bone remodeling 2.

Treatment Escalation Algorithm for Persistent Elevation

For stage 5 patients with PTH persistently >800 pg/mL despite medical therapy 2:

1. Verify phosphorus control (<5.5 mg/dL) 2
2. Increase vitamin D sterol dose to 10-15 mcg three times weekly 2
3. Allow 12-24 weeks for response, as severe hyperparathyroidism requires prolonged treatment 2
4. If PTH remains >800 pg/mL with hypercalcemia/hyperphosphatemia refractory to 3-6 months of optimized therapy, refer for parathyroidectomy 2