When do you usually order intact parathyroid hormone (iPTH) levels in patients with Chronic Kidney Disease (CKD) who are new to hemodialysis?

When to Order iPTH in CKD Patients New to Hemodialysis

For patients newly initiated on hemodialysis, measure intact PTH (iPTH) within 1-4 weeks after starting dialysis, then monitor every 3 months once stable, with more frequent monitoring (monthly) during any treatment adjustments. 1, 2

Initial Baseline Assessment

When a patient begins hemodialysis, establish baseline iPTH levels early in the dialysis course:

• Measure iPTH within 1-4 weeks after hemodialysis initiation to establish baseline values and guide initial management decisions 2
• This initial measurement should be accompanied by simultaneous assessment of serum calcium, phosphorus, and alkaline phosphatase 3
• The iPTH sample should be drawn at least 12 hours after any calcimimetic dosing if the patient is already on such therapy 2

Ongoing Monitoring Frequency for Stable Patients

Once baseline values are established and the patient is stable on hemodialysis:

• Measure iPTH every 3 months using an intact PTH assay as the standard monitoring interval 1, 3
• This quarterly monitoring applies when iPTH levels are within or near the target range of 150-300 pg/mL 3, 1
• Patients with iPTH levels at the lower end of the target range (150-200 pg/mL) may be monitored less frequently than those at the upper end 3

Increased Monitoring During Treatment

When initiating or adjusting therapy for abnormal iPTH levels, monitoring frequency must intensify:

• Measure iPTH monthly for at least 3 months after starting or adjusting vitamin D sterols or calcimimetics 1, 4
• Once the target iPTH range (150-300 pg/mL) is achieved and maintained, return to quarterly (every 3 months) monitoring 1
• During cinacalcet dose titration, measure iPTH 1-4 weeks after each dose adjustment, with no dose changes more frequently than every 2-4 weeks 2

Research evidence supports that monthly monitoring is superior to quarterly monitoring for achieving target iPTH levels—one study showed increasing monitoring from quarterly to monthly improved the percentage of patients reaching target from 25.4% to 40.3% 5

Concurrent Laboratory Monitoring

iPTH monitoring should never occur in isolation:

• Measure serum calcium and phosphorus within 1 week of starting or adjusting calcimimetics 2
• During vitamin D therapy initiation or dose adjustment, check calcium and phosphorus every 2 weeks for 1 month, then monthly 1, 4
• Once maintenance therapy is established, measure calcium approximately monthly and phosphorus at similar intervals 2, 1
• During active dose titration of calcitriol, serum calcium should be checked at least twice weekly 4

Target iPTH Range and Treatment Thresholds

Understanding the target helps determine monitoring urgency:

• Target iPTH for dialysis patients: 150-300 pg/mL 1, 3
• Initiate treatment when iPTH exceeds 300 pg/mL (assuming calcium <9.5 mg/dL and phosphorus <4.6 mg/dL are controlled) 1, 6
• iPTH levels <150 pg/mL warrant holding calcium-based phosphate binders and avoiding further PTH suppression to prevent adynamic bone disease 1, 3
• Severe hyperparathyroidism with iPTH >800-1,000 pg/mL may require consideration of parathyroidectomy if refractory to medical therapy 1

Critical Caveats

Several pitfalls must be avoided:

• Never target normal PTH levels (<100 pg/mL) in dialysis patients, as this causes adynamic bone disease and increases fracture risk 6
• The K/DOQI target range of 150-300 pg/mL may still be associated with low-turnover bone disease in some patients—one study found 88% of patients within this range had low-turnover bone histology 7
• iPTH measurement quality varies by assay; second-generation intact PTH assays are preferred over first-generation assays 8
• Marked changes in PTH levels should prompt therapy adjustment, not just values outside the target range 9

Practical Algorithm for New Hemodialysis Patients

1. Week 1-4 of hemodialysis: Obtain baseline iPTH, calcium, phosphorus, alkaline phosphatase 2, 3
2. If iPTH 150-300 pg/mL: Recheck every 3 months with calcium and phosphorus 1
3. If iPTH >300 pg/mL: Initiate vitamin D sterols or calcimimetics (if calcium/phosphorus controlled), then monitor iPTH monthly for 3 months 1, 6
4. If iPTH <150 pg/mL: Hold calcium-based binders, avoid PTH-suppressing agents, recheck monthly until normalized 1, 3
5. During any treatment adjustment: Monitor iPTH monthly, calcium/phosphorus every 2 weeks initially 1, 4